Want Dropdown Selection to Trigger Color Change

Rusty Java user here. Thanks in advance for the help!

In the form below, I need the user's selection from the drop down menu (Dropdown12)  in the Status column (selections are Green, Yellow, Red, N/A) to color that box the corresponding color. I'm running this script as a custom validation script in the Validate tab. I have the "Commit selected value immediately" box checked on the Options tab. 

This script turns the dropdown menu background to the correct color (except for black which isn't doing anything), but does not turn the box itself a color. Is what I'm trying to do available in Acrobat?

Thank you!

if (event.value=="Green")event.target.fillColor=color.green;

else if (event.value=="Yellow")event.target.fillColor=color.yellow;

else if (event.value=="Red") event.target.fillColor=red;

else if (event.value=="N/A") event.target.fillColor==black;

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