Sub Macro1()
Dim C As Range
Dim R As Integer, G As Integer, B As Integer
Set C = Range("A1")
C.NumberFormat = "@"
C.Value = "255,0,255"
R = 1 * Split(C.Text, ",")(0)
G = 1 * Split(C.Text, ",")(1)
B = 1 * Split(C.Text, ",")(2)
C.Interior.Color = VBA.RGB(R, G, B)
End Sub