Oh yeah, it's totally possible. Anything is possible if you just <rainbow> believe!! </rainbow>. Your options for coloring it would be 1) printing it in full-color sandstone, 2) making separate pieces and printing both, then putting them together, or 3) just making it one color and then painting part of it yourself.
Edit: Are you aware that they sell these signs online? It'd probably be cheaper and more efficient to just buy yourself one from Ebay.