Technique using custom bone shape

That technique using custom bone shape so that the colored mesh shows only in pose mode was super cool. Didn't know I could do that.

Just curious, but is this only to be used with single bone armatures ? Because say I have a snake/fish mesh for which am using a chain of more than 1 bones and the custom shape can only be applied to only 1 of the bones I presume. Where else is this feature of using colored bone groups and custom bone shapes useful for ?