I can't seem to change the background color on a form in a smartlist cell, from a groovy script

Summary: I am trying to change the cell background color from a groovy script. when I run the script, there are no errors, but the color doesn't change.

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I have a scrpt (see attached) the runs before save, and cycles through the grid. If it finds a data cell with an invalid account, smartlist combination, I want to change the color of the cell to make it easier for the user to see. I have a script which runs without error but doesn't change the cell color. I have no idea why any hlp would be appreciated.