GreenRange turns your buttons RED when abilities are out of range. Several addons do this, but GreenRange is very efficient at it. It's "green" because it's modern and efficient, not because of the color. :P If you really like green though, you can configure it for green!
GreenRange actually has a negative performance cost, because it replaces some really inefficient code in the default UI. It's not going to increase your framerate by more than 1, but still, it works so well that it actually improves performance vs. not having it.
If you profile range-checking addons like this, you want to look at CPU usage, not memory usage. OptionHouse can profile CPU, but its "%" metric isn't that meaningful because it's relative to the other addons you have running. "CPU/Sec" is the easiest metric to use. "CPU" is meaningful only if you a) do the timing yourself, say 60 seconds, and compare equivalent times or divide to make them equivalent, and b) /run ResetCPUUsage() first so the counting starts at zero.
There's no config UI yet, but you can use /run commands to change the colors, and the setting will be saved. These are the defaults: