Need help with coloring combo boxes

Kinetic ERP
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1

I am trying to finalize a product configurator, and trying to color mandatory combo fields “red” color. like if the combo box is not chosen its red and if a choice is made it turns to no fill or default color.
can some one help me in this, like an if then else statement…
if there is one - which level would i execute it (document rule, operation rule, or in designer level)
Thanks and regards

2

Epicor Version?

3

system version 11.3.100.10
release 2024.1.10

4

Web Configurator or Classic ?

5

web