In addition to the attributes described specifically for each element, the attributes: id, xref, class, style and href are allowed on every MathML element. MathML Fundamentals
<math style="border:1px" mathsize="100"> <mspace linebreak="newline" indentalign="center"></mspace> <mrow style="border:2px;padding:4px;border-color:red green black #ff00ff;"> <mrow style="border:2px dotted blue;"> <mrow style="border:2px;margin:4px;color:red"> <mrow style="border:2px; padding:2px;color:black"> <mrow style="border-right:20px;padding:2px"> <mrow style="border-bottom:20px;padding:2px"> <mrow style="border-left:20px;padding:2px"> <mrow style="border-top:20px;padding:2px"> <mrow style="border:1px;"> <mtext style="border:1px">FMath MathML</mtext> </mrow> </mrow> </mrow> </mrow> </mrow> </mrow> </mrow> </mrow> </mrow> <mspace linebreak="newline" indentalign="center"></mspace> <mrow style="color:red;border-right:20px;border-color:green"> <mrow style="border-bottom:20px;border-color:blue"> <mrow style="border-left:20px;border-color:#888888"> <mrow> <mtext style="border:1px">FMath MathML</mtext> </mrow> </mrow> </mrow> </mrow> <mspace linebreak="newline" indentalign="center"></mspace> <mrow style="border:2px;padding:10px;border-style:dashed;border-color:green;"> <mrow style="border:2px;padding:10px;border-style:solid;border-color:blue"> <mrow style="border:2px;padding:10px;border-style:dotted;border-color:#888888"> <mrow> <mtext style="border:1px">FMath MathML</mtext> </mrow> </mrow> </mrow> </mrow> <mspace linebreak="newline" indentalign="center"></mspace> <mrow style="color:red;border-right:20px;border-color:green;padding:10px;background:#aaffaa"> <mrow style="border-bottom:20px;border-color:blue;padding:10px;background:#ccccff"> <mrow style="border-left:20px;border-color:#888888;padding:10px;margin:10px;background:#dddddd;color:green"> <mrow> <mtext style="border:1px">FMath MathML</mtext> </mrow> </mrow> </mrow> </mrow> </math>