You should look for a 100% cotton twill material. It should have the feel of a pair of pants, for example, like Dickies work pants.
It is not always easy to find the combination of the right color and the right fabric.
If it is 100% cotton, you can dye it to the color you would like.
I just purchased our next bolt of fabric and it will not be quite as heavy.
There are benefits and drawbacks to either light or heavy fabric.
Heavy fabric, is much hotter to troop in, but may last longer. Heavier fabric is cool and more comfortable for trooping, but may not last as long.
It is really a matter of opinion. But everyone stays with cotton because it is screen accurate, easy to dye if needed and it breathes, it is much more comfortable.