Overall the functionality looks pretty good. Some thoughts in no particular order:

1. The selected color is shown as a circle colored border with white fill -- but that makes me think that the circle was showing the option to select white as a color. Can the selected color keep the colored fill but maybe add a thick black border to indicate the selection?
   

2. What determines if a group comes with a pre-assigned color vs doesn't? I created groups based on Sex or Genomic Profile availability:
   
   Male & Female have colors, and that I can understand since we define default colors for those values. But why does 'fusion' come with a color when 'mutations' and 'log2CNA' don't ?

3. I'm struggling with the symbol that appears for groups that don't have a defined color. The symbol (square with red diagonal line) makes me think of some sort of null value that needs to be fixed - in the screenshot above, the fact that 2 groups have that square with the red line and the other 3 groups have colors makes me think I have to assign colors to all groups or else they may not work.

Is there another symbol that would be more intuitive for 'you can select a color here but you don't have to' ? At the very least, perhaps updating the tooltip to say something like 'Optional: Select color for group to be used in group comparison. If no color is selected, a random color will be applied.'

4. When groups are shared, they are shared without their assigned colors:
   
   https://www.cbioportal.org/study/summary?id=gbm_tcga_pan_can_atlas_2018#sharedGroups=6081a1d3e4b015b63e9e78d0,6081a1e0e4b015b63e9e78d1,6081a1ece4b0242bd5d49ccf,6081a1ffe4b015b63e9e78d2,6081a20be4b0242bd5d49cd0,6081a42ae4b0242bd5d49cdc
   Is this intentional? I expected colors to come with the groups.

5. Why is the groups dropdown refreshing every time I select a group?