Calculated CSS color

Hello there!

I'm trying to build my first Intellij plugin which should highlight CSS classes with the calculated color (like what Intellij is doing when editing a CSS file directly).

I did the code to highlight the list of CSS classes in an HTML file, as you can see in the screenshot below, what remains now is to calculate the color of a CSS class.

I think it should be possible since that's what you're currently doing with the autocomplete of CSS classes, as you can see in screenshot below.

Could you please tell me how I could retrieve this calculated value ?
Thank you :)