Multi-column matrix color formatting

Hi!

I've create a matrix with multiple columns headers: Chemical, Level 1 and Level 2.  The row headers are Location and Date, the values are results.  

I've added a measure to conditionally format the results to color based on which Level it falls within - e.g:

>= Level 1 && < Level 2 = green

>= Level 2 = tan

I would like to color code the column headers reflect the above colors Level 1 (green) and Level 2 (tan)  so that it is apparent to the viewer which Level is being applied.  Unfortunately I cannot select individual column headers in the format section.  Has anyone accomplished this before?  is it even possible?  

I've included a screen shot of the existing formatting and what I would like to accomplish below:

Please let me know if you have any questions/comments/concerns.

Thanks!

CJ