100 Things You Never Knew About Resident Evil
86. The S.T.A.R.S. Outfit
For an elite group of military men and women, the Raccoon City Special Teams and Rescue Service sure do dress funny. Despite being a unified squad, they are surprisingly not uniformed. Of course, this is for design purposes - twelve solders in different colour coded gear is a lot more interesting (and easy to differentiate on the PS1's blockier graphics) than a dozen character models all in the same fatigues.
That said, the lore of Resident Evil does love to drop in little morsels for nerdy fans to chew on that explain little inconsistencies.... such as why Chris is wearing a totally different S.T.A.R.S. uniform when he sets off to Rockfort Island in Code: Veronica.
Apparently, during the two years that the team existed they had been trialling prototype uniforms and body armour, and this green-and-black get-up was the latest. So, presumably swiping it from the RPD before he got suspended there following the events RE1, Chris wears this new uniform to honour his fallen comrades. Who knows, this uniform might've been approved as the official S.T.A.R.S. outfit had the Mansion Incident not occurred.