Depending on how many colors and Themes you are talking about, use an IF...Then...ElseIF statement or a Select case Statement to assign different values to some variables, then format the cells using those variable's values.

This may help
Sub showColorIndexNums()
    Dim i As Long
    Worksheets.Add before:=Sheets(1)
    [A1].Value = "Color"
    [B1].Value = "Index Number"
    ActiveSheet.Name = "ColorIndex"
    For i = 2 To 58
        Range("A" & i).Interior.ColorIndex = i - 2
        Range("B" & i).Value = i - 2
    Next i
    ActiveSheet.[B:B].EntireColumn.AutoFit
End Sub