I'd start by picking a colour you really like, and then picking an 'accent' that compliments it... really anything goes on Corsairs...
It might help to think about their 'personalities' as well... are they closer to a Craftworld you like, or maybe a bit more on the Commorite side? Basically if none of the 'official schemes' work for you, it's entirely up to you.
I also have tended to pick schemes that go well with my other armies... so if you have others, that might factor into your decision somewhat (I have blue/orange Corsairs to compliment my black/yellow Ulthwe).
There's also the 'test model' approach - if you can work it down to two or three ideas, try them out and figure out which you like best and/or which will be the easiest to implement. Once you're a squad or two in, it's tough to realize that your scheme is too complex, or that you don't like it much.
Good luck!
Cheers,
The Good Doctor.