Combinations of mathcolor and mathbackground.
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"> <mrow> <menclose notation="box"> <mi>a</mi> </menclose> <mo>,</mo> <menclose notation="box"> <mi mathcolor="#FF0000">a</mi> </menclose> <mo>,</mo> <menclose notation="box" mathcolor="#FF0000"> <mi>a</mi> </menclose> <mo>,</mo> <menclose notation="box" mathbackground="#80FF80"> <mi mathcolor="#FF0000">a</mi> </menclose> <mo>,</mo> <menclose notation="box" mathcolor="#FF0000" mathbackground="#80FF80"> <mi>a</mi> </menclose> <mo>,</mo> <menclose notation="box"> <mi mathbackground="#80FF80">a</mi> </menclose> </mrow> </math>
Author: Bruce Miller