Auto Color whole column when found text "Sunday"

[Kenji]

The code below works well also. However, I got 2 problems here.
First, I manage to find the word " Sunday", then color the cell below that Sunday. However, I need Excel auto find out Sunday and color that particular columns for me, for example, Sunday found and color start from cell(L55) below that Sunday up to more cells(L59), Range("L55:L59").
Second, I only manage to find first Sunday, I wish the system keep find and keep color untill it found that rows blank, so I using this code.
'Encountered blank cell in row 2, terminate search
If Len(Cells(2, LColumn)) = 0 Then
MsgBox "No matching date was found."
Exit Sub

I attached the excel files with sample, I really hope someone can help, these problems delay me 2 months d. Thanks alot !

<script type="text/javascript">
Sub AutoColor()
 
    Dim LDay As String
    Dim LColumn As Integer
    Dim LFound As Boolean
    
    On Error GoTo Err_Execute
    
    'Retrieve date value to search for
    LDay = Sheets("Rolling Plan").Range("B4").Value
    
    Sheets("Plan").Select
    
    'Start at column B
    LColumn = 2
    LFound = False
    
    While LFound = False
    
        'Encountered blank cell in row 2, terminate search
        If Len(Cells(2, LColumn)) = 0 Then
            MsgBox "No matching date was found."
            Exit Sub
        
        'Found match in row 2
        ElseIf Cells(2, LColumn) = LDay Then
             
            Sheets("Plan").Select
            Cells(3, LColumn).Select
            
       With Selection.Interior
        .Pattern = xlSolid
        .PatternColorIndex = xlAutomatic
        .Color = 40000
        .TintAndShade = 0
        .PatternTintAndShade = 0

    End With

            LFound = True
            MsgBox "The data has been successfully copied."
            
        'Continue searching
        Else
            LColumn = LColumn + 1
        End If
            
    Wend
    
    On Error GoTo 0
    
    Exit Sub
    
Err_Execute:
    MsgBox "An error occurred."
    
End Sub
</script>