Slow copy paste in Excel vba - arrays

Question

I have the below code and find that copy-pasting is slow and the interior colour is slow as well.
I am trying to deal with this code with 700,000 rows + 120 columns of data.
Any suggestion to improve the speed.
Currently, it can take me more than 20 mins to finish this row of code.
Application.ScreenUpdating = False
Application.DisplayAlerts = False
Application.Calculation = xlCalculationManual
Application.EnableEvents = False
Application.DisplayStatusBar = False
For i = keycolumns + 2 To ILcol + 1
'Result.Cells(1, resultcolumn).EntireColumn.Insert
rColumnLetter = Split(Cells(1, resultcolumn - 1).Address, "$")(1)
iColumnLetter = Split(Cells(1, i - 1).Address, "$")(1)
IL.Range(iColumnLetter & "1:" & iColumnLetter & ILrow).Copy Result.Range(rColumnLetter & "1:" & rColumnLetter & ILrow)
colNum = Application.WorksheetFunction.Match(Result.Cells(1, resultcolumn - 1).Value, PL.Range("1:1"), 0)
Result.Cells(1, resultcolumn) = Result.Cells(1, resultcolumn - 1) & " Postload - " & colNum
'Result.Cells(1, resultcolumn + 1).EntireColumn.Insert
Result.Cells(1, resultcolumn + 1) = Result.Cells(1, resultcolumn - 1) & " Comparison"
ColumnLetter = Split(Cells(1, resultcolumn + 1).Address, "$")(1)
Result.Range(ColumnLetter & "1:" & ColumnLetter & ILrow).Interior.Color = RGB(146, 208, 80)
resultcolumn = resultcolumn + (2 * (i - i + 1)) + 1
Next i

Answer 1

In my experience it is better to avoid operations directly on the sheets. What I would do is:
create an array variable
resize the array so it can hold all the data
populate the array with the actions currently included in your 'for' loop
print the array into the sheet
The final result would be close to this:
public sub populateArray()
dim arr_data() as Variant
dim numberOfRows,numberOfColumns,currentRow,currentCollumn as integer
currentRow = 0
currentCollumn = 0
numberOfRows = 10
numberOfColumns = 10
redim arr_data(numberOfRows,numberOfColumns)
for currentRow to numberOfRows
for currentCollumn to numberOfColumns
arr_data (currentRow,currentCollumn) = "TEXT"
next currentCollumn
next currentRow
with activesheet
.range("A1") = arr_data
next with
end sub
Please note that I did not test the above code, feel free to adjust it to your needs.