Depending on what kinda of rainbow one you want, nope
If you want a sectioned rainbow one, then yes, it could cost more because Im using 6 different colors.
(red orange yellow green blue violet)
But! If you want a rainbow one like the one up there *points* That is just using one type of yarn and I can find the colors usually in tyed dyed yarn like that.
Or, if you want like a specific rainbow, like blue pink and purple, (bi colors) then I could only charge you the extra 2.50 for the blue because I only have one blue color and its not the right shade for the bi colors. Understand?
Also, if I dont have the color you want, then I buy my yarn from walmart so the price for yarn that I dont have is ALWAYS 2.50. If I already have the color, then I wont charge you extra.