Here is the starter file for the rainbow.(if you want a single arch
just replace the modulo node with a subtract scalar)
Good luck!

calico:it's still Mr_L's file,unaltered except for the above mentioned
changes.Size in the fall off section from 10000 to 2500 and you
know where to find cloud depth and Invert Profile i guess,anything
else remained the same.But if you still want it i can post it tomorrow.
Mr_L.:

just noticed your post and i'm eager to see those.