This ticked me off.
I was leaving a rehab clinic office after dropping off my wife and got onto the elevator with an African-American mother and her son, who appeared to be 12 or 13. He was wearing the t-shirt pictured above.
That’s a racist message. If I were to wear a shirt or a cap saying “White is my happy color,” it would be viewed by any non-whites I encountered as a veiled insult, and correctly so. This is no different. Thanks to Barack Obama and George Floyd, anti-white racism is considered sufficiently justifiable, indeed deserved, that blacks can wear this shirt with impunity. Google even covers for them: “What does black is my happy color mean?” it asks. “This is the color you are most comfortable and most confident in and the one that reflects your character. I wear black a lot and experts say that wearing black means that you are confident, powerful and success driven. I’ll take that. Black is also perceived as the most attractive color,” Google says in answering it’s own question (bolding theirs).” Riiiiight. The kid was making a fashion statement.
To state the obvious, if I had worn a “White is my happy color” shirt, it would be regarded as a white supremacy boast, and properly so. (Notice of Correction: I had written “There are no ‘White is my happy color’ shirts for sale.” Commenter Steve-O helpfully informs me that there are indeed. I dare him to wear one in my neighborhood…) I came within a filament of saying something to the mother. This is how you raise a racist. This is how you guarantee racial divisions and tensions forever. This is how American blacks lose potential political and social allies who are not going to be sympathetic to complaints about “microagressions” from the same people who make me read racial insults on their shirts.
Sure, it’s another “black lives matter” rhetorical trick: “Hey, saying black (skin) makes me happy doesn’t mean that I have anything against white people!”
Now you’re insulting my intelligence too.
Ethics Alarms 
I thought black was merely slimming. :D. I think a shirt like that is basically engagement bait. There is no way anything good could come from engaging with someone in this situation. There really isn’t any point and engaging with anyone over a t-shirt. The fact that they’re wearing it should tell you you’re not going to change their mind.
White can’t be a happy color. We’re past “it’s OK to be white”, any expression of white existence must be less than ambivalent.
In the interest of peace and good will, how about a t-shirt saying:
White is a neutral color. On the front.
And so is black. On the back.
Colors are reversible. This will put an end to racial disharmony once and for all.
That’s as good a solution as anything else…
As a similar experience…
On Saturday, my wife and I encountered a young woman – likely high school or early college aged – wearing a t-shirt that read “Resist Gender Norms”. My wife considered saying something to her about it, but then realized the young lady was baiting someone (anyone, really) into an argument. We said nothing and let her maintain whatever mental confusion around which she enjoys wrapping her existence.
The t-shirt encountered by our host is more sinister than what we saw, but I’m guessing both were seeking the same result…confrontation.
To be technically correct black is the absence of color. To have color, light waves must be reflected back.
If black is now a color then we are all people of color.
https://printerval.com/white-is-my-happy-color-white-color-t-shirt-p1614797?spid=401912532&campaign_id=698134631&msclkid=ef9aadf8c5671d047448c8eadcb2509e&utm_source=bing&utm_medium=cpc&utm_campaign=Printerval.com_US_BingAds_Pmax_All%20products_06%2F08&utm_term=2330071297976610&utm_content=US%20All%20Products
BTW, you are mistaken.
About THAT. I’d love to know who buys that t-shirt.
I don’t think the shirt is inherently racist. My first assumption would be goth or emo. They were very insistent on wearing black themed clothing. Something a kid would wear to get one past his parents, who would otherwise be concerned about all his talk about the darkness in his soul.