Of krell modes a README file says:

    % zgrep -A 6 "Moving the" /usr/share/doc/gkrelltop/README.gz
    Moving the mouse over the krell panel causes a tooltip to appear,
    showing more info such as the PID and processor usage percentage.
    The refresh of the top three will be suspended for about 2 seconds,
    when mouse first moves over.

    Upon clicking, the krell will rotate between CPU, Memory, and IO monitoring
    of the processes. Upon rightclicking, the config panel will come up.

But when the krell "rotates" between the three modes, they all look the
same.  Usually the numbers and rankings differ between modes, but
without using the mouseover tooltip there seems to be no visual
indication of which mode the current numbers and ranking represent.

Possible visual distinctions include: a header, e.g. "CPU", etc.
(takes space), or different background colors by mode, or a three-state
icon illustrating the mode, or three icons one of which is highlighted
as a sort of radio-button icon, and so forth.

HTH...