calc-highlight-selections-with-faces

calc-highlight-selections-with-faces is a variable defined in `calc.el'.
Its value is

nil

Documentation:
If non-nil, use a separate face to indicate selected sub-formulas.
If option `calc-show-selections' is non-nil, then selected sub-formulas are
shown by displaying the rest of the formula in `calc-nonselected-face'.
If option `calc-show-selections' is nil, then selected sub-formulas are shown
by displaying the sub-formula in `calc-selected-face'.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.1 of Emacs.