Glad I could help!
OK I thought you said it was winter :) I doubt he is intentionally, though if he's shedding the old hair may be lighter. If it's super warm and he is too hot you may want to clip, though I would be more inclined to wait for him to shed.
If it's been warm and sunny he may be sweating more and having more direct sunlight too.
Do you know exactly what the DNA testing was? A lot of people advertise "homozygous black" and stuff but any black, bay, or brown based horse can be homozygous black.
If you are so inclined, take some GOOD pictures, at different times of years. Overall pictures, close ups, everything, anything that shows his color well. Post them in the colors and genetics thread. There are a lot of good people and several REALLY good people who can help with colors. It's the next best thing to a genetics test and free.