That's a great catch on your part. I read somewhere that something like 8 percent of men and a smaller number of women have some form of color vision deficiency, which is way more common than people think. A lot of folks just assume the client will see what they see, and that's where the money gets lost. Free online checks are okay for a rough guess, but they don't always handle different screen settings or print conditions well. Paying for a tool that lets you test every version of the design before it goes to press feels like cheap insurance, honestly. Your $60 story is a good reminder that we're not designing for our own eyes, we're designing for the client's eyes, and sometimes those eyes work differently.