Excel - VBA Comparing cell values to each column's average

I'm trying to prepare a code in vba for excel. For each month there is a list of values, each month is listed in a separate column, multiple values are listed below each month.

What I wanted to do is change the color of each cell which value is 4 times smaller than the month's average. So far my code looks like this, each average is calculated like I wanted it, but i can't seem to figure out how to get it to compare the cells only to one column's average, not to all of them consecutively - like it does now.

Sub MonthAverage()
    Dim Data As Variant
    Set Data = Selection
    Dim rows As Integer
    Dim columns As Integer

    rows = Data.rows.Count
    columns = Data.columns.Count

    Dim average As Double

    For j = 1 To columns
        average = 0#

        For i = 1 To rows
            average = average + Data.Cells(i, j)
        Next

        average = average / rows

        For Each cell In Data.Cells
            If cell.Value <= average / 4 Then cell.Interior.Color = RGB(0, 0, 255)
        Next

        MsgBox average 'just to make sure I got the averages correctly
    Next
End Sub