Both List and Spread will accept an array of cell background colours. This should either be a vector with the same number of elements as the number of columns in the data, or a matrix which has the same shape as the data array.

nltBCol'red' 4 '#BB7B27'       © Orange

You can give the colours as short mnemonics (these are case sensitive), as indices into the standard 16-colour palette (0=black), or as hex strings.