I've been wanting to know this too! I haven't done it, but I plan to do it. Here's a good tutorial: https://www.hunker.com/13425081/how-to-affordably-and-easily-color-landscaping-bricks-and-other-concrete
Spray with concrete/masonry dye and it will work! I’ve done a lot of work with it.
No but remember if you spray them you will have to do them every year
Mason dyes have a UV resistance to the pigments suitable for outside use.