Dynamic conditional formatting ranges by slicer selections

I'm trying to set different conditional formatting ranges based off slicer selections in a gauge. We have two different departments with separate goals for the same value field. I'd like to be able to show different ranges for red, yellow, green based off department selections from the slicer. I read another post and might be heading down the wrong path, but they had suggested setting up a color measure - but now if I go to format style by field value, that measure is grayed out and I can't use it . Am I on the right path, or is there a better way to accomplish this? I'm fairly new to PowerBI, but this is where I'm at currently at whith building the color measure