There are lots of pictures of Children's Pythons (Antaresia childreni) on the web.
You might also look at photos of Spotted Pythons (Antaresia maculosa), since some of the snakes sold as Children's Pythons in captivy are actually this species.
They should be any color other than combinations of tan/brown/white/off-white. They do have a lot of iridescence to the skin, but they certainly don't have any "rainbow" colors.
If you post a decent photo here, we could certainly tell you what it is.
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Chris Harrison
San Antonio, Texas