You can set the background colour for individual cells by setting the Range.Interior.Color property.
How, though, do you clear it? Simply setting it to white (0xFFFFFF) clears the grid lines too. Is there another property you need to use to set the grid lines? (I have investigated Borders but that is, as I expected, just for the formal border lines.) Is there a particular way of clearing the Interior.Color property instead of just setting it to white?
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