Excel: Insert colon in military time column?

We have a excel work sheet, there is a very long column that states the time for an event. We need the time in the format below:


Original
hhmm

Needed Change
hh:mm


This is my original code below for other changes, if it could be added for range G:G for example that would be great!

Thanks!

Sub replaceText()
Dim c As Range, rg As Range
Application.ScreenUpdating = False
Set rg = Intersect(Range("A:A"), ActiveSheet.UsedRange)
For Each c In rg.Cells          'Only search column L
    Select Case c.Value
        Case "B"              	'Old value
            c.Value = 3         'New value
            
        Case "BAP"              'Old value
            c.Value = 3         'New value
            
        Case "BB"               'Old value
            c.Value = 3    	'New value
            
       

        Case Else               'Do nothing
    End Select
Next

Application.ScreenUpdating = False
Set rg = Intersect(Range("C:C"), ActiveSheet.UsedRange)
For Each c In rg.Cells          'Only search column L
    Select Case c.Value
        Case "M"              'Old value
            c.Value = "Male"         'New value
            
        Case "F"              'Old value
            c.Value = "Female"         'New value
            
            
        Case Else               'Do nothing
    End Select
Next
Set rg = Intersect(Range("D:D"), ActiveSheet.UsedRange)
rg.NumberFormat = "@"
For Each c In rg.Cells          'Only search column D (ARADMDT)
    If c <> "" Then c.Value = Mid(c.Value, 5, 2) & Right(c.Value, 2) & Left(c.Value, 4)       'Change date from yyyymmdd to ddmmyyyy
Next
End Sub

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