Yes. When you define a KPI, you can specify display rules. A display
rule says "if the value is in the range nnn-mmm, then override with
these colors & font options and/or this image."
Then on a dashboard, you add either a label or an image, and specify a
KPI to "control" it. The value of that KPI will determine how the
label or image is displayed.
See "Using KPI Display Rules to Override Text or Graphics" in the
Designer book.
(I should update the doc. to point to this section from the part where
I talk about speedometers. They're alternative approaches to the same
issue. So that is on my list of things to do.)