It's my understanding that this isn't currently possible. If so, consider this a feature request. If not, then I suppose it's a question and learning exercise. :)

I'd like to be able to assign a color to a large number of servers/metrics by regex in order to visually differentiate between even and odd numbered servers.

One way might be through the color function on a per metric basis like would be done in graphite directly. For example:

color(ops.site.web.*[13579$].*.*.gets,"green")
color(ops.site.web.*[02468$].*.*.gets,"blue")

I'd like to use this where there are so many metrics that the colors don't help to readily identify changes in groups of metrics. At the same time I don't want to combine those metrics so that I can still visually identify individual outliers.

Thanks again for Grafana!