A word of advice: Do not, under any circumstances, let your husband take photos for your blog. This could happen to you.
While we're examining CJ's tush, have a look at these photos and feel free to guess what color the little guy is. The photo on the left was taken at 20 months; the one on the right, at 30 days.
His sire is grulla, and his dam is gray (born black/summer black, or possibly very dark bay). His topside grandsire was grulla and granddam black. On the bottom, his grandsire was black and granddam gray (birth color unknown.) Other horses in his lineage include a bay, a liver chestnut, a blue roan, more blacks and summer blacks, and more grays.
Below is another 30-day photo. More current photos may be seen in this post. A few resources to help include EquineColor.com, which does a nice job of explaining the basics of color genetics in horses; Batty Atty Acres' color articles, which include good photos of more unusual colors; and this Horse Colors site, which offers some very helpful photos, if you can put up with all the annoying ads.