The single RGB zone is an indicator of the currently-selected setting for mouse sensitivity. Colors can be customized, of course. Clicking on the button below the mouse roller cycles through four options, which are programmed to 400, 800, 1500, and 3000 DPI by default.
As to my own usage impressions, I use a fingertip grip for the most part, and a mouse like this fits my style well. Not an ultra-lightweight mouse, the mouse is still quite easy to move around with a fingertip grip at 96 grams, though movement of the KATAR PRO will be much smoother with a quality mouse surface (naturally).
The mouse buttons are satisfyingly clicky, the wheel has a grippy feel and a pleasantly segmented roll, and overall I have zero complaints about my usage experience.