I have a few lighter colored Chanel flaps (off white medium hybrid, '05 light beige/cream caviar Jumbo flap, dark beige caviar hobo w/ gold h/w, and dark beige medium flap w/ silver h/w)... my most used summer bag is my caviar hobo for sure.
I haven't carried my off white hybrid as much, but the '05 Jumbo has held up just fine.
I know for a fact that I wouldn't purchase a light colored lamb flap (my mom has one and it just sits unused), but caviar is okay.
A caviar flap is relatively easy to maintain, so you should consider it (and maybe buy some Appleguard).
I plan to add one more light colored flap - the '09 light beige medium with gold h/w - because I think it's the perfect spring/summer bag and it's stunning!!
I also use a
Gucci Britt/cream trim tote as a more expendable spring/summer bag.
Hmm, and as far as other Chanels go, my Bronze Cotton Club tote gets a lot of spring/summer use, as does my Dark Gold 227 reissue, dark brown medium/Jumbo and Khaki Baby Cabas!
I don't really carry black bags much in the summer.