What if Shampoo puts on Akane-shade black dye, and starts acting like
Akane? Then we see Ranma falling for Shampoo.

I think Ranma would be a little more loyal to Akane (although he might
find himself liking Shampoo a little too much as he tries to get Akane
back to normal).  And I get the feeling Shampoo wouldn't need to put on
Akane-blue/black, just dye remover.  The other two colors are general
stereotypes: blond (or curley blond?) for airhead, and white for
wisdom/intelligence.  They aren't linked to any character.  So maybe
purple = violent bimbo, and Shampoo always uses it.  Who knows what
Shampoo would be like if the dye was removed?  Hmmm... I wonder if dye
remover would have any effect on Cologne's long, WHITE hair... but she's
plenty old enough to have white hair naturally, and the thought of
blond or purple dye on her is too frightening to contemplate.

I think there is a typical way this story could go:
Ranma spends some of the story figuring out what the hell is going on,
while things are getting worse and worse (ie Ukyou dyes her hair, Nabiki's
financial empire collapses and the dojo has no money, blah blah), and them
some trying to get the dye-remover on everybody affected.  The proprtions
of these two lengths are variable, with a common one being: he figures out
fairly fast, but something happens to the dye remover and he has to quest
to get some more (or the ingredients, etc.).  Of course, that might be
a blueprint of what to avoid.  Arg! I type too much.

Oh, and shouldn't the title be "Any Colour You Like"? ^_^

>From the Dark Side of the Moon,
josh