In the original series, Max wears a white shirt, coverd by a red button up shirt with a floral design. He has grey hair and blue pants as well as black shoes.
In Ben 10: Alien Force and Ultimate Alien, Max's appearance did not change except for his blue pants have changed to brown, he has more wrinkles, a slightly darker shirt, and whiter hair.
In Ben 10: Omniverse, his appearance has not changed except for his brown pants have now changed to white. He also has more wrinkles. His white shirt that he wore under his red button up shirt has changed to black. His shoes are now grey at the top and black at the bottom.