It would be nice if the next version of Sonar had user definable red and yellow zones for meters like Cubase. I'd like to be able to set red at -10 db and yellow at -18 db so it's easy to tell when I've got things in the ballpark.

While waiting, if you are feeling adventurous, segmented meters are images stored in TTSRES110.dll. I believe Duckbar provides a way to modify these images.

The only time I even look at SONAR's meters is to check if I've got signal coming in on a channel prior to hitting Record. It's just that they're too small.
 
Fortunately, there are plenty of third-party meters that support K-metering. The K-20 scale is pretty close to what you're asking for, except that the yellow zone starts at -22 dB, red at -18 dB. I use K-14, so I know I'm in the pocket on the master bus when the indicator's bouncing around or just below the 0 mark, which is actually -14 dB.
 
There is also a K-18 scale that's right about where you want to be, but it's not part of the original K-system spec and therefore not available on most meters. BlueCat Audio's DP Meter Pro is one that lets you define any scale you like - but it's $79.