I don’t think that forced choice can give accurate results if a substantial number of people perceive green and blue as being non-adjacent - i.e. there exists a color between green and blue (turquoise/cyan/teal).
Otherwise it’s like asking people whether a color is red or yellow, when it’s clearly a shade of orange.
Orange is closer to green than blue but I wouldn’t say that it’s a shade of green. It’s just orange.
No it's like asking people whether a color is red or green, when it's clearly a shade of yellow.
https://en.wikipedia.org/wiki/Color_wheel#/media/File%3ALine...
Your website is not talking about "levels" of colour.
It's asking "is this blue or green", not "is this closer to blue or closer to green".
The question (1) "is this blue or green" has three valid answers: blue, green or neither.
The question (2) "is this closer to blue or green" only has two valid answers.
I would assume that with these types of surveys, the first thing to do is to qualify the proper categorization of the question.
Sorry to say, but to me it seems that almost all of the confusion in the discussion here is because you're asking question (1) (which has three valid answers) but expecting an answer from (2) (which indeed has two valid answers).