We all love colorful towels, but if possible I would suggest you only use white towels. The following is why.
Firstly, white towels can not hide dirt. If you care about your personal hygiene,you should keep your towels as white as possible.
Second, white towels are easily to wash and handle. You can use hot water, H2O2 and other laundry detergent, even Sodium Hypochlorite, so called liquid bleach.
Third, the white towels are environmental friendly. Since white towels only through bleach process no further dyeing process, very short time in dye house and use less water. Colored towels will use much of dye and towels keep in the solution very long time and use much more water to cleanse them. So same weight grey towels, colored towels are heavier than white color towels, more dark more heavier, because of dye added.
Fourth, the cost. At the same weight, white towels are cheapest. Because dyes long processes are costly, especially nowadays the dyes must be environmental friendly and free from harm. White towels are very cheaper than colored towels.
So choose and use white towels if you love your family and the environment of earth.