Compare neighbours
Look at a small colour area next to two different backgrounds. Notice whether it appears warmer, cooler, brighter, or quieter without changing its actual printed value.
Inspect the page hierarchy
Identify where the strongest contrast appears and whether it supports the reading order. Colour can organise attention or scatter it across unrelated details.
Keep a physical sample
If you are studying your own design, make a modest print proof. Record the paper and output method so the comparison remains useful later.