As always, short question won't help you as much you need.
When you talk about dimension text color, You have give some thing like below
If(FieldName = 'Smart', Green(), If(FieldName = 'Poor', Red(), LightCyan()))
This condition you must use from Dimension and go to Text colour then paste over there and hit ok. Here, How expression works as If FieldName has Smart value or name then text colour shows as green same as Poor text colour shows as Red or else LightCyan. This should work as you required
May be one option is go to colour tab and use persistence colour check box
Or else, Try this in BG colour from Expression