Hi Dominic,
Have a look at a similar question : https://in.mathworks.com/matlabcentral/answers/11513-display-matrix-values-with-color-coding
You could change the colormap in the code to:
colormap = [1 1 1;1 0 0]; %[W R]
as you use only 2 colors(white or red) and 2 categories of values (<1 or >1) fill the cells.
Hope it helps!