Suppose we want a cell, that has numbers in blue, to switch to red
type if that cell value becomes negative.
Make sure that the correct cell is selected.
From the Format menu choose conditional formatting . . . and a
dialogue box will appear.
Set the condition Cell Value Is to be less than 0 as shown in
the illustration.
Click the Format button on the dialogue box to set the
appearance that the cell is to have if the condition is met.
Notice the limited range of format change that is possible. You
can only set the font colour, the fill (background) colour, and the
cell border colour.
Click OK, and then OK back on the Condition box.
Make the cell become negative, then positive, then 0, etc. Checking
that the conditional formatting is triggered correctly.
More Powerful Conditions
It can often be very useful for the format change to trigger on a
calculated value not a specified value.
In the
More Beads sheet I set conditional formatting to trigger if a
cell matched its integer part, that is had no fractional
part.
I changed the second input box from "
between " to " equal to ".
Typed in =INT(A2) in the third input
box. The = is necessary because a calculation is required.
Clicked the Format . . . button and
made my choice, etc.
Note
When a cell is replicated, not only
its formula but also its formatting is copied. This includes
conditional formatting.