Why? Scoring. 2048 has a score that's also a number. So if you colorize only based on keywords, you'll color the score too. And that's bad.
Edit: I'd happily take patches, suggestions, or pointers to documentation on how to do the colorization properly. Email in profile.
Correction: Steve's above code is another implementation.
Colorization is against Zachary Kanfer's (zck) implementation in MELPA, which is here:
And don't miss David Thompson's (davexunit) Guile version mentioned below.
I'd much prefer to see these core code packages in the spotlight over the OP's mere colorization link.
Here's a screenshot after I mashed the arrow keys until I lost:
And the source (warning, messy):