For some time, it has been rumoured that Thomas takes a photo of Carol Brady to the hairdresser. As this photographic evidence shows however, there are significant differences between the two haircuts. Tom's hair is a shade darker and Carol's has slightly more body - possibly due to the two using different shampoo and conditioning products; Carol uses the Johnson & Johnson brand, while Thomas uses the natural oils from his body which Lillian harvests for him using a custom made spatula.
Exhibit A
Carol’s hair is a lighter shade with highlights.