A nice touch is the black hem that stays flat without curling.
Kesha Rainbow Tour 2018 Black Cotton All size S-5XL Gift For Fans T-shirt KK1701
You will notice the lack of branding here, which makes it super subtle.
New Popular Rainbow Kitten Surprise The Friend Love Freefall Men All Size RM191
I love that this tee is unbranded, letting you dress it up or down easily.
Mens Funny T Shirts Rainbow River Cool Nature Graphic Tee for Men
You will find that the 3XL drapes nicely without being flimsy.
Mens Skull Rainbow Puddle Funny T Shirts Cool Graphic Tee for Men
The 3XL runs a bit generous, so you can size down if unsure.