Nice comments... but the pedant in me (I think he's taking over) had to ask: What distinct colour is a rainbow?
It's not any distinct colour. It is made up of multiple colours, blended one into the next. Colours, plural. The oil on water descriptions is fantastic. But "Hair that was of no distinct colour" implies a bland wash of a single, neutral shade. I think it might be because you've used the singular form for the first sentence phrase, but then in the second sentence phrase you describe an image which is made up of shades, plural. Try: "Hair that shimmered every colour at once, appearing like the sheen of oil on water."
I gotcha. I am not sure I agree, but my perception may be wrong. The problem with reading your own crap is the "kill your darlings" tedious cliche. You kinda read what you wanna read. I'm putting that in brackets next to the sentence until I've got the actual/intended meaning clear.
