Hi mpatpc,
The coloring on p-values, conditional formatting as it's called in JMP, is based on how small the p-value is. By default, P-values are colored red if they are between 0.01 and 0.05, and p-values are colored yellow if they are less than 0.01.
For platforms that support correlation (such as Analyze > Multivariate) conditional formatting is applied to values on the basis of the degree and direction of correlation.
I hope this helps!
Julian