Refactor legend color code.
Refactor legend color code.

ucscXena/ucsc-xena-client,acthp/ucsc-xena-client,ucscXena/ucsc-xena-client,ucscXena/ucsc-xena-client,ucscXena/ucsc-xena-client,acthp/ucsc-xena-client,acthp/ucsc-xena-client,ucscXena/ucsc-xena-client