The cause of the error is that oFF.Result is a String value, which has no attributes. That's why the "." notation doesn't work. The thing associated with the formfield that does have a .Font.Color attribute is the oFF.Range member.
If you just try to set the color, you'll get a runtime error saying that it can't be changed because it refers to a protected part of the document. To be successful, you have first unprotect the document, change the color, and then reprotect the document. Try this:
Code:
Sub CountValues()
Dim A_Count As Long
Dim B_Count As Long
Dim C_Count As Long
Dim oFF As FormField
A_Count = 0
B_Count = 0
C_Count = 0
For Each oFF In ActiveDocument.FormFields
If oFF.Type = wdFieldFormDropDown Then
ActiveDocument.Unprotect
Select Case oFF.Result
Case "A"
A_Count = A_Count + 1
oFF.Range.Font.Color = wdColorRed
Case "B"
B_Count = B_Count + 1
oFF.Range.Font.Color = wdColorBlue
Case "C"
C_Count = C_Count + 1
oFF.Range.Font.Color = wdColorGreen
Case Else
End Select
ActiveDocument.Protect _
Type:=wdAllowOnlyFormFields, _
NoReset:=True
End If
Next oFF
MsgBox "A - Selected " & A_Count & vbCr & _
"B - Selected " & B_Count & vbCr & _
"C - Selected " & C_Count
lbl_Exit:
Exit Sub
End Sub