Battery use - phone signal indicators

I posted this on the CM7 thread but thought anyone with GB experience might have the answer.

I was wondering if anyone knows the differences in colors for the usage 'phone signal' part of the chart.
The one under battery use when you 'blow up' the top graph and get the color bars below.
I know when in airplane mode its black, when no signal it's red. The other three colors I've noticed is beige, yellow, and green.
I'm assuming that's in order of strength with beige worst and green best??
But it doesn't seem to fit with the signal strength I really have. Is it also using data as part of that? google services? android? dialer?
The reason I ask is relating to battery life.....some of the other statistics don't seem to help much and was hoping it would shed some insight.

Thanks