destielhallow:

Well then anon, I’m glad that you ask. Here is the gif of Dean’s shirt in the promo.

As you see, the first thing is, among Dean’s collection of plaid shirts for 10 seasons, the one that Dean wore during his “burger date” with Cas in 10x09 is a brand new one. There’s a website dedicated to the Winchesters’ wardrobe so you can check it out to confirm my statement. Since the shirt is new, viewers tend to notice.

The second thing is the color theme choice for the shirt. It’s made up of various shades of purple, red and blue (I also see some white lines). But you know, when the colors are blending together to make up a plaid shirt, our eyes tend to perceive the color differently. For example, blue + red = purple, red + white = pink, purple + red = magenta. Since there’s too little red, all i can see in Dean’s plaid shirt are such color: light purple, magenta (purplish-red), and dark blue. Unless I’m colorblind unknowingly. Coincidentally (it’s not a coincidence), it’s also the color of this pride flag. (I give you a hint, it starts with letter “B”.)

To be honest, those colors above are not Dean’s primary color theme choice (which are Red, Blue, and Green). Separately, sure. But together, well then, we have a message from the wardrobe department for Dean’s character which is… god knows what except that Dean in S10 chose to wear a shirt in 50 shades of purple whose symbol is for “desired love” according to neven-ebrez on a “date” with Castiel.

You already know that purple is the color associated with queers (whose attraction are towards both genders) right?

I could say those colors above are more associated with Cas more than with Dean. Those are color theme in 9x06, Heaven Can’t Wait, a heavy Destiel episode where Dean also wanted Cas to ditch his job at gas-n-sip and go on an “investigation date” with him that involved an angel who killed people (Cas) who just got their heart broken by their love ones (Dean). 

Though how could I know, I’m just a fan watching the show while obsessing with colors from Dean’s shirt. Besides, I haven’t watched the episode yet. I didn’t know in which context that made Dean put on the plaid shirt with such color. Though compare to the “Mark of Cain” darker than black shirt also showed in the promo, his other shirt in the “date” with Cas is more interesting and noticeable.