The old brain-bender about 'how do we know that blue looks the same to everyone' is pointless. There's no way and really no reason to find out. We have our conventional labels and when we say 'point to the red square' everyone can point to the same square each time. Well almost.
Rarely is there disagreement in identification of primary or secondary colors. And we can identify shades pretty accurately too. Once I was doing a color match with the additive RGB scale of 0-255 for each value and I matched the two areas within 3 total points difference. 3 points among 16,000,000. Our eyes can be pretty impressive.
But the linguistic task gets fuzzy quickly. What's navy blue? What's dark blue? Sky blue? Baby blue? Powder blue?
If you want to know what other people said in a study described on the Dolores Labs Blog just check the map below. Don't get mad when you disagree. Maybe you're the one that's wrong.
(click image to enlarge)
Now play with the labels. This page allows you to type in a color or a specifier and see which shades were called what. If you type orange only those shades that were called orange or have <orange> somewhere in the name will show up in the wheel.
Several years ago a friend of mine was looking at some shirts in a nice store. The salesperson walked up and asked if he needed help.
'Yes. What is this colour?' he asked. 'It's not on the tag.'
She looked at the shirt then checked the tag. 'Sorry' she responded. 'I'm not sure exactly what it's called.' She shrugged figuring it wasn't a big deal that she didn't have such specific information. 'Is there anything else?' she asked.
'Well can you just tell me?' he asked again.
She looked confused. 'Sorry' she repeated. 'I don't have that information anywhere. It's not listed and I don't know where to find it.'
'Can't you tell just from looking?' he asked.
'Look, the names change from brand to brand. So your guess is as good as mine.'
'No it's not' he said. 'I'm colour-blind.'
She looked horrified. 'Ohh I'm so sorry. It's green.'
He laughed and told her not to worry about it. Knowing him I think he was hoping she'd misunderstand.