Shinigami Death Punch (also called Shini Punchi by a large part of the fanbase) is a Webcomic that started on a Japanese site around December of last year. Even though there isn't an official translation into English yet, a variety of fan transcriptions - and a bit of creative guessing by the fans - have gained it something of a fandom among English-speakers now.The comic revolves around two teams of shinigami, White Team and Black Team, performing missions in the mortal world to collect souls and bring them across the river Styx and into the Underworld. Most of the plot arcs revolve around Purple, the newest member in the White Team and basically a complete failure at being a shinigami.
Bookworm: Yellow, as evident by the fact that we see his books more often than his scythe.
Color Coded For Your Convinience: All of the introduced Shinigami thus far are known primarily by their color, which also indicates their rank. It does make telling the characters apart pretty easy.
Cool Shades: Apparently part of the shinigami uniform, at least during missions (and appropriately making everything on missions seem more Badass). Ignored most of the time by Pink, whose look is more adorable than badass.
Custom Uniform: Purple and Pink, who have strayed so far from the "uniform" that they aren't even obviously wearing a uniform anymore.
Dark Is Not Evil: The Black Team is not actually the bad guys. In fact, recent updates suggest that, if anyone, it's the White Team.
Dark Secret: Purple being half-human. It's not a secret to the readers, but it is to the other shinigami, and the repercussions of it getting out would no doubt be catastrophic.
Plot Pants: Plot hoodie, in Purple's case. He gets his hoodie at the end of the first plot arc, marking him as the official main character, and whatever else he ends up wearing, the hoodie always comes back. Turns out it doubles as Magic Pants, which explains why an ordinary hoodie can survive hellfire.
RainbowMotif: Most of the colors of the rainbow have been introduced at this point, as well as White and Black.
In fact, Pink is the only character that doesn't fall into this trope right now.
Rose-Haired Girl: Pink, of the "Cheery and Optimistic" variety. She's not anyone's love interest (yet), though.
As of Pink's backstory arc, it's really not that debateable anymore.
Shinigami: Obviously. Of the Psychopomp variety, in this case — possibly intentionally, since the comic contains multiple references to Greek mythology. They act as both escorts and guardians of the afterlife, but don't actually cause the deaths. Or, at least, they're not supposed to.
Ship Tease: Constantly with White and Purple. Nearly every scene with them plays on this in some way, especially once White starts getting protective.