Iserson overanalyzes this factor in "getting into a residency" and its unfortunately an issue that many of us therefore worry about. I think its importrant to remember that you are interviewing the program as much as they are interviewing you. If the color of your suit (assuming it isn't orange/bright red/etc) is a significant factor in the program's decision would you really want to work there for 5+ years?
By this point, you shouldn't need to be told to not wear dirty, scuffed, or wrinkled clothing though we have all seen the rare exception. The color of your suit is far less important than you may think. I have met attendings and residents who have interviewed in maroon, navy, grey, beige, brown and black. Their advice: don't wear what you know you aren't comfortable in! A good fit and comfort will let who you are shine through.....and the color will become as non-memorable as it should be.