It depends on the outfit I’m wearing and the color of the bag. Some outfits look better with a Kelly and other outfits look better with a Birkin. Also, some colors are better as a Kelly while others are better as a Birkin. For example: I always see light blue and light green colors as Kellys, but I see dark blues and greens as Birkins. Reds, browns and neutrals can be either.
Funny that you mention dark blues & green are a better option for Birkins.
I happen to own a shade of blue in an exotic & a dark green in box both of which are Kellys
so one's perception of which colors look better in Kelly/Birkin is interesting.
I think Kelly/Birkin work with most outfits but depends on how you "rock it" & like both bag styles
from jeans to suits (depending upon size might make a difference)