There's no built-in function for this. How about a macro? ; such as
Sub CountFontColour()
y = ActiveCell.Font.ColorIndex
x = 0
For Each cell In Selection
If cell.Font.ColorIndex = y Then
x = x + 1
End If
Next cell
Range("B1").Value = x
MsgBox "Count = " & x & "."
End Sub
, which requires the "test cell" to be the active cell.
For proper macros dealing with colours 'n' stuff, see