I don't think it comes in silver. Onkyo's site lists only black.
The 5100 and below come in both colors.
If silver is a must-have, the TX-SR606 receiver (which is the receiver in the 7100, and is fairly close to the 6100's receiver with minor differences) comes in silver. You could buy the 606 and a separate company's 5.1 speaker package. Might stretch your budget, but it would get you a silver receiver (and maybe speakers, too.)
Otherwise, the 6100 is a good deal.