If you portray a character as only ever actually purchasing yellow socks, and over the space of 12 years the audience sees him buying yellow socks a dozen times or so and when asked what colour socks he likes he says “I only like yellow socks”, then you are fully expected to think that he only likes to buy socks that are yellow.
That is fine. However…
Consider if every time he has been asked or it has been implied that he might like socks that are not yellow it has been in a hostile environment and admitting to liking red socks might culturally seem like a weakness.
Consider how the environment he grew up in made him believe red socks were culturally wrong and he maybe therefore just sticks to yellow because hey it’s not like he doesn’t like yellow socks too right?!
Consider how many times he glances at and full on checks out red socks when there are some nice ones available.
Consider how, when his best friend wears red socks he struggles to compute anything else in the room and eye-fucks the hell out of those red socks to the point that his brother is an awkward moose about it and has to clear his throat or change the subject on numerous occasions.
Consider how when the red socks are forcibly taken away from him he usually goes and impulse purchases some yellow socks. But over the years it seems to satisfy him less and less.
Consider how he is so desperate for red socks by this point that he’s stopped pretending so hard to his brother that he doesn’t want the red socks and is spending most of his time trying to get his best friend back to him who happens to have the exact particular red socks that he has been pining for for years.
Consider how, after a bunch of life changing events he starts openly admitting that even though in the past he said he only liked yellow skittles for instance, he now actually admits to liking the blue, green and red ones too and that his brother just has to learn to deal with it because he’s now just done and impatient with having to hide it all, “grow up Sammy”.
Consider how he starts actually saying outloud that there are some things that he hides, that he sublimates…
It may not be explicitly canon yet that Dean is bisexual, but its a hella implied in the subtext.
Coupled with the fact that Dean has repeatedly and canonically admitted to hiding aspects of himself that he thinks are culturally seen as unmasculine eg. taylor swift, cake, fancy shampoo etc. To the point that in season 2 Sam actually tells him that he seems to be “Butch” and “Overcompensating”. Just saying. This is not new. This is not ‘Dabb ruining my favourite character’ or whatever, this has been there all along.
Coupled with the fact that in 12x05 he actually said the words “sublimation is kinda my thing”.
Coupled with the fact that 12x11 was a whole episode dedicated this. To explaining to the audience that Dean deep down is not who he portrays himself to be due to all the baggage he has accumulated over the years, heavily relatable to the whole ‘red and yellow socks’ metaphor. Also hella relevant in the whole ‘who are you’ discussions this season with the brainwashing, Alesha, Cas, the heart v brain v memories discussion. It is repeatedly shown that it is the heart that is who you really are, not the memories.
What I’m saying is it might not be canonically explicit yet but it sure is leading that way and this is not a new thing, it’s been in the subtext since season 1, it’s just only now coming to the surface as we are at the point in the story where Dean is starting to learn who he is and reconcile the old and the new within himself and accept himself for who he is.
This is not out of character. It is entirely IN character. You just have to have looked at who that character really is beyond the facade since the pilot to see it.
And hell, if a guy likes red and yellow socks why can’t he have both?