You can buy grout colorants, which are powders you add to color grout...others can tell you where to buy them, no one around me carries them, but online mosaic stores have them also.
Or-you can color your grout with acrylic paint. My method is to add the paint to the dry grout and then add water so I dont get it too soupy, others may do it differently. and lastly, you can use slightly watered down acylic paint to do a wash over already set grout. Using paint may not hold its color as well outdoors. And only use acrylic or water based paints. oil based paints and the water in grout dont mix.

Use out door pants !!It will not fade as much.I have some that have been pant 3 yers still looks good.

Home Depot and Lowe's has a wide variety( like 20 or more) of colors. If you don't have either close Google grout colrants, many sites have them. I usually use the one's from HD and Lw's unless I need a custom color. And always make extra when doing it custom because getting it the same twice is virtually impossible!!! Believe me I've tried, doesn't happen. Hope this helps....

Cathy where do find them at lowes? I have looked and looked and if I ask I get that are you nuts look from the help. I have all but given up. I dont have a HD, only a lowes.....

I just used my acrylic craft paint, glooped a bunch into the grout after I made it, mixed it real good and mooshed away, have also just painted the grout with the craft paint afterwards too(watered down)to stain it the color I want. Since I am a terrible painter...always wanted to try tole painting, but am Really bad, I am glad to have found a use for these paints!!!

Thank ya'll for all the info. It may be awhile before I get a chance to use this information, but eventually I'll get to it.