What does the shading around some 48 series keys indicate?

[Joe Horn]

I've always wondered the same thing, so I'm glad you asked. One possible hint at the thinking of the designers can be found in the 48G Series Quick Start Guide, which has three diffeernt names for the above right-shifted keys:

(1) Right-shift CHARS is called "The CHARS feature" on page 2-7 and 2-8.
(2) Right-shift MODES, MEMORY, and STACK are called "Utility Environments" on pages 2-14 and 2-15. Left-shift EDIT is also included in that set.
(3) Right-shift 1 through 9 (including UNITS!) are called "Application Environments" on pages 2-12 through 2-14.

So it would SEEM that the designers put the light green shading around the right-shift key and the 1 through 9 keys to highlight the officially-named "Application Environments". IMHO it seems strange to call the UNITS menu an "environment", since it uses the ordinary stack display's "outer loop", but hey, at least the keyboard shading agrees with the Quick Start Guide.