Well I find it easier to use a set of color / banner which is already designed to fit my forum color scheme.
As it is now, the current set is useless for me because the colors used doesn't match at all.
So, yes I need to create my own and I've already seen the resource you're mentionning. But it's easier to choose a color when you can see the whole palette, rather than have to type it.
This is why I would like to know if it is possible to change the default one, and how ? But maybe, if the default set is changed, it may be revert back after an upgrade ?