Conditional Formatting Based on Rules Set by Slicer

In the dax formula, start with a variable to harvest the slicer sélection using selectedvalue. 

In a second Var you put the conditions.

• You will have 

Measure = 

VAR _sel = SELECTEDVALUE('Table'[SlicerColumn])

VAR _value = SUM('FactTable'[Value])

VAR _result = SWITCH(

    TRUE(),

    _sel = "A" && _value > 15, "red",

    _sel = "B" && _value > 8, "red",

    _sel = "C" && _value > 12, "red",

    "black"

)

RETURN _result

And you use this dax for the cond formatting of the font.