Blues and greens work well on most horses. (My favorites are turquoise or teal, but that's because my horse is red.) Jewel tones would look good on him, as would colors like lime ice or a pale yellow. He's dark enough that just about any color would look good on him, so go wild. Just make sure the color looks good on you, too. :)
As far as tack goes, that's partly a personal preference thing, partly a style thing. The ultra-light oil tack is going out of style. I like a medium oil for just about everything, because while you might never set a trend in it, you're not going to get outdated next year, either.
Learning never stops