No, "iridescent" is quite right. It means "having or exhibiting iridescence."
"Iridescence," in turn, is "a lustrous rainbowlike play of color caused by differential refraction of light waves (as from an oil slick, soap bubble, or fish scales) that tends to change as the angle of view changes."
Again, I cite www.m-w.com (the Merriam-Webster web site) as my source. Note that th
I guess we'll have to disagree. I'm using the Oxford English Dictionary and it doesn't consider rainbowlike to be a word. It uses rainbow-like in the definition, but that's two words.