Option Explicit
Sub abc()
Dim i, j
Cells.Interior.ColorIndex = xlNone
For j = 1 To [a1].End(xlToRight).Column
For i = 2 To Cells(1, j).End(xlDown).Row
If Cells(i, j).Value < Cells(i - 1, j).Value Then _
Cells(i, j).Interior.Color = vbGreen
Next
Next
End Sub