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I know you have an unconditional love for VBA. And, that’s why we have a macro code to apply color to all the blank cells from a selected range.

Sub ColorBlankCells()
Dim rng As Range
Set rng = Selection
rng.SpecialCells(xlCellTypeBlanks).Interior.Color = vbRed
End Sub

When you run this code it will check each cell from the range and then apply red color if a cell is blank.