XML or Data Merge fields?
It's hard to see from the screen shot.
But this is the only information I've ever known about yellow in tables. I wrote it up for InDesign Secrets in 2007
If you see a yellow highlight in table cells, it is an indication that you have decimal numbers that can’t fit in the table cell with their decimals lined up correctly. Instead of lining the numbers up according to the position of the decimal tab stop, InDesign will shift the numbers to the left or right so that they are visible within the cells. However, the yellow highlight indicates that the alignment to the tab stop is off. To get rid of the yellow highlight, as well as line up the numbers correctly, select all the numbers in all the cells and then open the Tabs panel. Move the decimal tab stop until the highlight disappears.