Whatever floats your boat - but the Drumtraks you posted is black, with black knobs. The JP-6 is a greyish colour, with light grey knobs, and multicoloured silkscreening, buttons and LEDs. I think adding a brown would make it look like a dog's breakfast, but hey - try it! Even if I'm right, a little wood won't have cost that much, and of course I'm usually wrong. Just ask my ex-wife. ;)
If I were to deviate from the existing JP-6 aluminum, I'd like to get some slabs o' metal as thick as those wood sides. I think that would look awesome! Maybe even chrome plated or something!
I need to get some substantial slabs of wood like that to replace the cheap sides on my Korg MS2000. The thin strip of wood on the right side of the keyboard actually broke.