Change the proportions
Use the same three colours in several ratios. Notice which becomes dominant and how the others behave as accents. The palette's effect belongs to the distribution as much as the colour values.
Place text in context
Test headings, ordinary text, and small labels separately. Check readability at realistic sizes and avoid using colour as the only distinction when information matters.
Make a material sample
Try the design with the intended paper or output method. Texture and reproduction can alter the relationship. Keep a labelled sample so the result can be evaluated later.