DNA is the color white as long as its found in a mass. I guess we have a lot of white objects going through our bodies. To the human eye, it looks like glue.
1 Additional Answer
Deoxyribonucleic acid or DNA is a large molecule and can be described as being multicolored. However, it is so tiny to the naked eye it is pretty much invisible. If you break it down to the most basic parts it is a carbon sugar. That can be black, white or clear. You can find more information here: http://en.wikipedia.org/wiki/DNA