Coloring The Joints Between Flagstone?

Putting color in Portland Type II Cement to fill the joints between flagstone is not a good idea.

Joe from California asked:

I am putting in a flagstone walkway on a concrete base. I have layed the stones using a type S mortar to set in place. My question is what type of colored grout shoud i use?

Answer:

Dear Joe, We never recommend using color. We have never seen a color in bricks or stone that lasts more than 2 to 3 years. It streaks too much after the sun tears it up. Indoors coloring works well, but not outdoors. We just got done talking to a landscape architect and he says he never will use coloring.

Hope that helps,

David and Hans