Translucent Rainbow 🌈

In case you might wonder, with translucent colors it appears OK to use 1x1 pieces because it's unnoticeable/invisible if the corners of translucent 1x1 pieces protrude when they're slightly rotated instead of being perfectly aligned. Similarly, with translucent colors it appears OK to have some vertical cracks along the arch's outer/top edge and inner/bottom edge because any light that passes through such cracks simply blends in with all the light passing through the translucent pieces.

Currently, if you want to actually build a physical model like this one, you need to use round 1x1 plates instead of square ones for the colors Translucent Bright Green and Translucent Purple. You might consider Translucent regular Green as an alternative to Translucent Bright Green, but I think that Translucent regular Green doesn't harmonize/blend as well as Translucent Bright Green does with the adjacent colors Translucent Light Blue and Translucent Yellow. Of course, an alternative is that the rainbow could be 2 studs thick, in which case you could use 1x2 plates which already exist in the colors Translucent Bright Green and Translucent Purple. But I think that a thickness of 1 stud is somewhat nicer structurally, and it should be less expensive.

Also, currently it's difficult to obtain the round tiles which are at the ground in colors that work well together. One possibility might be Light Bluish Gray.