Cell is Not Recognized as Filled If Filled Using VBA

I have a cell that is highlighted yellow if a checkbox is checked.

I want to restrict printing if this cell is still highlighted, but my macro is not working.

My code to highlight (fill) the cell based on whether a checkbox is checked is as follows:

Sub CheckBox76_Click()
If ActiveSheet.Shapes("Check Box 76").ControlFormat.Value = 1 Then    
    Range("G54").Interior.Color = vbYellow
    MsgBox ("Please enter the CFDA number in the highlighted field (G54).")
Else    
    Range("G54").Interior.Color = RGB(221, 235, 247)
End If
End Sub

Code to check if cell is filled in and restrict printing if it is.

Private Sub Workbook_BeforePrint(Cancel As Boolean)
Dim rRng As Range
Dim rCell As Range
Set rRng = ActiveWorkbook.Sheets("Assign_FI$Cal_Project_Code").UsedRange
If ActiveSheet.Name = "Assign_FI$Cal_Project_Code" Then
For Each rCell In rRng.Cells
    If rCell.Interior.Color = vbYellow Then        
    Cancel = True        
    MsgBox "Please fill in highlighted cells before printing."
  End If
Next rCell
End If
End Sub