specify color(s) of identicons

I’m trying to restrict the color of my identicons to a single color or a choice of several specific colors. I’ve tried wp-identicon plugin, but it seems to malfunction–after a couple of weeks, all my identicons are the same.

I’m wondering if there might be a simpler route to restricting the color of the images output by WordPress itself. Ideas?

I’m not great at php but can generally get results after a few trials. I’m using a custom child theme of twenty ten on the site in question.