it's most definitely NOT dumb!
I bet at least half the members of tPF have doubles (and triples and quadruples!) of the same style in diff colors
If you find a style that works well for you, and find yourself using it more than any other style, it only makes sense that you'd want to add a second one in another color.
I happen to love the MJ stam and currently own three of them (two quilted and one soft leather), but have owned as many as five at one time! As mentioned here already, Balenciaga fans tend to purchase multiple colors of the size/style that works for them. The Chanel Flap, Rebecca Minkoff's Morning After, Chloe's Heloise and Paraty -- I'm sure if you roamed around tPF and into the various designer sub-forums, you'll find this is a pretty popular topic of conversation and a peek at some of the collections scattered across the forum, would reveal that this is a pretty common trend!