Format: EditHighlightColor red green blue alpha,
Example: EditHighlightColor 1.0 1.0 1.0 0.5,
Purpose: Color of the EditBox's Marked Text Box. Alpha should not be 1.0 because it makes the marked text unreadable. The alpha value can be skiped then it is 1.0.
Used in: EDITBOX, GLUEEDITBOX, SLASHCHATBOX