There is a difference between perception and categorization. You perceive the difference between salmon and fuchsia regardless of whether you have a word for them or not. You might refer to either color as pink, not because you failed to perceive the difference but because you don't particularly care about communicating the difference.

It's like measuring with a ruler. If you have mm notches then you'll be more likely to describe one thing your measuring as 31mm and another as 29mm, whereas if you have only cm notches then you'll probably say one is just over 3cm and another is just under 3cm. In the second case, you're measuring with a less accurate tool because you don't care as much about accuracy. Hell you may say they're both about the same size if that 2mm difference is insignificant enough. But regardless of how you communicate the length, their lengths exist and you qualitatively perceived them.