All personalizing on our towels is done with dye sublimation. It's the best method for microfiber as it doesn't affect the properties of the towel, and won't scratch the surface you are trying to clean. What dye sublimation does is essentially it will dye a localized area of the towel with pretty much any color. I say pretty much because it can't do one color, white. The reason white can't be done is that since we are re-dyeing the fibers of the towel, we can't remove the original dye of the towel. For example, a yellow towel is actually dyed yellow at the factory. If I try to put a white logo on it, the white dye would just make the yellow towel "lighter" in those areas, but not white. You can also think of it like painting a picture, if you mix white with yellow, you just get a lighter shade of yellow. In fact the ink manufacturers don't even make a white ink for dye sublimation. So the way we get around needing white ink/dye is to use a towel that is white. This way the white in your logo will actually not be printed and that will allow the white of the towel to come through.
Really dark towels, such as black can't really be done with dye sublimation either. If you have a black towel you won't be able to put, lets say, a light green design on it. Since the light green dye will mix with the black towel, it will still show up black. If your looking to do a towel that isn't white, we suggest going with a light shade of towel. For example, grey will work, but it needs to be light grey and the only color that should be printed onto it is black. When you are dealing with a towel that isn't white, it is best to make your logo/design use only black ink to avoid any color matching issues.
There is one way to get a logo/design that is black, and that is to do a full coverage print of a white towel. If you take a white towel and print the complete area of the towel with black, and whatever color logo, you can make it work. The only downside is that the other side of the towel will still be white. For an additional cost you can sometimes get the back side printed black as well. For our plush towels we can only print the low pile side. The plush side won't sublimate properly due to it's thread length. Only the tips of each thread will be dyed, and it won't look very good (see pictures below).
So in summary, dye sublimation does have it's limitations, but if you stay within it's limits, you'll be able to produce a product that is vibrant and durable.