No, black is not the only acceptable funeral suit. In fact, these days, I truly wouldnt be surprised if someone showed up to one in a NBA jersey. If you want to look your best and most respectful, a black suit is perfectly acceptable, and unless I am mistaken, was the standard for funerals many years ago. Today, most people would agree that a dark suit, either in charcoal grey or dark navy blue is what to go with. A solid coloured suit is preferable if you have one. As for the shirt, white is the way to go. If you dont have a white shirt, light blue is acceptable as a substitute. I would never, under any circumstances, wear a patterned shirt (unless it was a herringbone style, blue on blue or white on white kind of thing) and even then I would only do that as a last resort. A dark solid colored tie finishes it off, as do black shoes. A simple white linen pocketsquare is just fine also. I think the goal is to look somber, respectful, and draw as little attention to your clothes as possible. Im sorry you will have to go to a funeral at all.