This guide is for anyone looking at a color menu that says "Rainbow - Will Vary" and wondering what will actually arrive. Rainbow filament is one strand of plastic that slowly changes color along its length, so a rainbow filament 3D print picks up whatever stretch of color the printer is feeding while it builds your piece. We cannot choose which colors land where, and no two prints come out the same.
We offer Rainbow on 25 designs, from a $5 Bone Shark to the $35 Rose Snake, and it never costs more than a solid color. Below we explain where the colors come from, why size changes the result more than anything else, which designs carry the option, and how to order a pair that looks like it belongs together. Pick Rainbow on a long or large piece, where the filament has room to change color, and treat the pattern you get as part of the gift.
What Rainbow Filament Is, and Why the Menu Says "Will Vary"
Most of our prints use a solid filament: one spool, one color, start to finish. Rainbow filament is made differently. The maker blends colors into the strand as it is produced, so red fades into orange, orange into yellow, and on through the spectrum before the cycle starts again.
Each color runs for a long stretch of filament before it blends into the next. A small print can finish inside a single color, and a large one can use enough filament to pass through two or three.
The color is in the plastic itself. Nothing is painted or dipped, so the color will not chip or rub off at the joints. What you see on the surface runs all the way through.
It is the same premium PLA as our solid colors. A rainbow dragon is as strong, as flexible at the joints, and as sensitive to heat as a black one. Care is the same too: keep it out of hot cars and sunny window sills.
"Will Vary" is on the menu because the product photo shows one print, made from one part of one spool. Yours will come from a different part of the spool, so the photo shows the kind of result you can expect. It is not a preview of your piece.
How a Rainbow Filament 3D Print Picks Up Its Colors
A 3D printer builds a piece one thin layer at a time, from the print plate upward. Every layer uses a little more filament, and the color feeding into the nozzle drifts slowly as it goes.
Where the print starts decides the palette. If the spool happens to be in its blue stretch when your piece begins, it starts blue and drifts toward whatever comes next. The next order off the same spool starts somewhere else.
Transitions usually show as bands or patches. Because layers stack, a color change often appears as a band across the body. On wide, flat pieces the change can land partway through a layer, so one side of the piece shifts before the other.
The blend is soft, not a hard line. Rainbow filament fades between colors, so you get a stretch of in-between shades rather than a clean stripe. That soft edge is what makes a rainbow print look like one object rather than parts glued together.
We cannot aim any of this. Asking for the head to be purple is not something the process allows, and we would rather say so now than have you wait for a piece that cannot be made.
Size Decides How Many Colors You See
The single biggest factor in a rainbow print is how much filament it uses. Small pieces use very little, so the color barely moves. Large pieces use a lot, so the rainbow has room to travel.
Keychains and Micros often come out in one color, or one color with a hint of the next. The Bone Shark and Bone T-Rex keychains, both $5, are good examples. Choose Rainbow on these for a random single color, not a full spectrum.
Mid sizes such as the Skeleton T-Rex in Regular ($12) or the 11.5 inch Crystal Dragon ($10) tend to show two colors with a blend between them. This is where rainbow starts to look like rainbow.
Long and large pieces are where rainbow filament earns its place. The Rose Snake, sold in one long size at $35, the CinderSnake in Large ($25), the 24 inch Crystal Dragon ($25) and the Skeleton T-Rex in XL ($35) use enough filament to pass through several colors from end to end.
If you are torn between two sizes and want the rainbow effect, go up a size. If you want a random single color at the smallest price, the small sizes do that well.
Which Designs Come in Rainbow, and What They Cost
Rainbow appears as "Rainbow - Will Vary" in the Color menu on 25 designs. On every one of them it is the same price as Single, Dual or any other color choice for that size. You pay for size, not for color.
Skeleton dinosaurs
All eight skeleton designs offer Rainbow: the Skeleton T-Rex, Spinosaurus, Raptor, Stegosaurus, Triceratops, Ankylosaurus, Pteranodon and Mammoth. Each comes in Baby ($5), Regular ($12) and XL ($35). The full set is in our dinosaur collection.
Dragons and snakes
The Crystal Dragon runs from a $5 Tadling to a 24 inch piece at $25. The Winged Crystal Dragon comes in Tadling, 9, 13 and 18 inch sizes, and the Winged Crystal Tadling is $7, or $8 with a keychain. The Rose Dragon is $12, or $20 with its egg, and the Dragon Egg set runs from $5 to $45 depending on size and whether the egg is included. The plain Tadling is $5 in Crystal or Rose style. The two snakes, the CinderSnake ($10 Baby, $25 Large) and the Rose Snake ($35), are the best rainbow pieces we make, because their length lets the color travel. You can see them all in the dragon collection.
Axolotls, sea creatures and farm animals
The Axolotl with Legs comes in Rainbow or Pink Mix, from a $1.75 Micro to an 8 inch Mega at $15. The Axolotl with Line on Back comes in Rainbow or Like Pictured, from a $1.00 Micro to a $15 X-Large, with a $7 Keychain size. The Smiling Axolotl is $15, the Happy Turtle is $12, and the Hermit Crabs run $8, $12 and $25, with a separate choice of white, brown or black shell. The Highland Cow is $7, and the Stuffy Cow runs from a 2 inch Small at $5 to a 6 inch Large at $14.
Two close relatives
The Unicorn offers Pastel Rainbow as a hair color, at $5 for Regular and $12 for X-Large, and the Lip Balm Holder comes in Rainbow for $4.
Many of our classic six-size animals, such as the standard dragon and axolotl, have no Color menu at all. You type the color you want in the Custom color box. If you would like rainbow on one of those, ask us through the contact page before you order and we will tell you how it is likely to look at the size you want.
Rainbow, Dual, Single or Surprise Me: Four Different Choices
The Color menu on most rainbow-capable designs offers four or five options, and they are easy to confuse. Here is what each one means for rainbow filament buyers.
Single is one solid color. Name it in the Custom color box and that is what you get.
Dual is two solid colors in one print. You can say which color goes where, and we follow it where the design allows. Choose this if you want control over the two colors.
Rainbow - Will Vary is the gradient filament described above. You choose the effect, and the spool chooses the colors.
Surprise Me means we pick the color for you. Choose it if you want to be surprised by the choice itself, not only by where the colors fall.
The skeleton dinosaurs also offer a Girl Colors option. Our custom color guide covers how to write a color request we can print exactly.
Ordering a Matched Pair or a Set in Rainbow
Parents buying for siblings and collectors building a set often ask for two rainbow pieces that match. Rainbow filament makes that difficult, and we want to be clear about it before you order.
Two rainbow prints will never be twins. Each starts at a different point on the spool. Even two pieces printed back to back will differ, because the second begins where the first left off.
Ordering together gets you the closest match. Put both pieces in one order and say in the Custom color box that you want them as close as possible. We can then print them from the same spool, one after the other, so they share a palette even though the bands fall differently.
If an exact match matters, choose Single or Dual. Two children who notice every difference will be happier with the same solid color. Rainbow suits people who like having a piece nobody else has.
Adding to a rainbow set later is fine. A new piece will not match the old ones exactly, but rainbow pieces sit well together on a shelf because they share the same kind of soft blend. That is harder to say of solid colors from different spools.
Common Questions About Rainbow Filament 3D Prints
Can I pick which colors appear on my rainbow print?
No. The colors depend on where the spool is when your piece starts printing, and we cannot steer that. If you need specific colors in specific places, choose Dual and name both.
Does rainbow filament cost more?
Not at our shop. On every design with a Rainbow option, the price is set by size alone and matches Single, Dual and Surprise Me.
Will the colors fade?
PLA holds its color well indoors. Like any colored plastic, it can fade after months in direct sunlight, so a shelf out of the sun keeps a rainbow print looking the way it arrived.
Why does my rainbow print look different from the product photo?
The photo shows one print from one part of one spool. Yours came from another part, which is what "Will Vary" on the menu means. A color we did not expect is normal. A crack or a joint that will not move is not, so if that happens, write to us through the contact page with your order number and a photo.
Choose Rainbow Filament When the Surprise Is the Point
Rainbow filament is the one color option where you give up control and get a piece nobody else has in return. It works best on long and large designs, where the color has room to move, and costs the same as any other color.
If you want a sure result, choose Single or Dual. If you want a snake that runs through the spectrum, or a skeleton dinosaur that fades from one color into another, choose Rainbow and go up a size.
At Cosmic 3D Creations, every rainbow piece is printed to order in Como, Texas, from the part of the spool that happens to be feeding that day, then flexed joint by joint before it is packed. Printing takes 1 to 3 business days, Economy shipping is free on orders over $35, and you can order online and pick up at our Canton Trade Days booth, Booth 4268 and 4269, October 1 to 4.