It does seem a bit silly, and I will never leave quality or performance on the table for appearance, but all things being more or less equal I will pick the card with the cleanest,most "mature" aesthetic when I can.
Case has no windows and I have no interest in color coordination, but an angsty, edgy looking graphics card can be downright fugly.
XFX had some real winners on the AMD side with their 3xx family of cards, Sapphire had some real winners with their Nitro line of 480/580 cards, and EVGA has always produced respectable looking NV cards.