Colours

Each part of an equation is coloured separately, so a cell reference can be told from a name, and a name from its units, at a glance.

What each colour controls

Main: The expression itself: operators, brackets, and mathematical symbols such as ∑. Black to begin with.
Cell ref: Cell references, as drawn by Ref. Blue to begin with.
Name: Names found for cells, as drawn by Name. Blue to begin with.
Unit: Units, drawn to the right of the equation by Unit. Green to begin with.
Numeric: Numbers — both the constants written into the formula and the values pulled in by Value.
Function: Names of functions that have no symbol of their own, such as round.

Which colours are offered

Only colours that render identically on your machine and through the equation service are listed. That is what makes the preview in the panel a reliable guide to what will appear on the sheet.

Find these under Settings → Colours, at the foot of the panel.