Color-Coded Secret Identity

Everyone recognises Captain Superhero! He wears a blue cape, a red tunic, and green tights! And no-one suspects he's the mild mannered Steven Ulysses Perhero...who always seems to wear a blue jacket, red shirt, and green pants.

Hmm...

This is where a superhero's Secret Identity wears clothes that somehow match his superhero costume, in order to make him easier for the audience to identify.

Compare Astonishingly Appropriate Appearance, especially if he always dressed like that, but didn't choose their costume colours. If a Shapeshifting superhero wears the same colours in his superhero identity because of the clothes he's wearing, that's Morphic Resonance.

Examples of Color-Coded Secret Identity include:

Anime and Manga

Usagi's first school uniform looks very similar to the outfit she wears as Sailor Moon. They both have a white shirt/bodysuit with a blue sailor collar, a red bow on the chest, and a blue pleated skirt.
The Samurai Pizza Cats' civilian outfits were so similar to their mission gear that it was often hard for the viewer to tell which they were in. Lampshaded at least once.
In Tiger and Bunny, Kotetsu's Powered Armor is black, green, and white. His casual clothes? Black slacks, green shirt, and white vest. Barnaby also has similar color coding, but he has the excuse of not actually having a secret identity.
- The casual clothes of the heroes tend to be similar in colour to their costumes (Pao Lin in yellow, Nathan in red/pink, Keith and Ivan get blue/purple-ish shades). Karina is an exception, wearing warmer/darker colours than her skimpy blue outfit as Blue Rose. Possibly intentional, given how uncomfortable she is with her hero persona. Even Lunatic gets in on this as, when we see Petrov at the end of episode 9, he's wearing a grey suit with a blue-and-green patterned tie, similar to the colours of his costume.
The Pretty Cure franchise takes this to ridiculous lengths since Yes! Pretty Cure 5 as they not only wear color-coded civilian clothes, most of them have color-coded hair. The only one defies this trope is Ako/Cure Muse of Suite Pretty Cure, who wears pink and blue despite wearing black at first then going into yellow

Comic Books

Golden Age and Silver Age Clark Kent always wore a blue suit with a red tie. (Also seen in Superman: The Animated Series.)
- Lampshade Hanging in Smallville — Clark favoured wearing a blue shirt and red jacket...and that's why he became known as the Red-Blue Blur before he started wearing a costume.
- When Electro-Superman was split into Superman-Red and Superman-Blue, the businesslike Clark-Blue wore a grey suit with a blue tie, while the more relaxed Clark-Red wore an open-necked red shirt.
Golden Age Bruce Wayne frequently wore blue and grey outfits, and Dick Grayson wore red and green.
- They actually tried to avert this in the first season of Batman: The Animated Series and have Bruce Wayne not wear clothes the color of Batman's outfit. Due to color palette limitations, that meant he spent a lot of time wearing a rather ugly brown suit. In later episodes, Bruce usually wears a dark suit and Dick wears a red sweater vest. Barbara Gordon favoured purple, perhaps reflecting Batgirl's costume in the 1960s TV series.
In the current DC Comics and dating at least from the 1970s Shazam TV series, Billy Batson always wears a red shirt with a yellow collar.

Live Action TV

The Power Rangers, a fact occasionally lampshaded.
- The best example of that comes from Power Rangers Dino Thunder when Tommy, returning to action, approaches Conner, Kira and Ethan and tells them he has to run to the mall - he checked his closet and realized he had a complete lack of black.
- The early seasons took it Up to Eleven, where the characters seemed to own nothing that wasn't in their ranger color. Some actors have said they couldn't stand the color anymore after their time on the show. Getting to keep their secret identities was a major point of Fridge Logic, as the five teenagers who obsessively wore nothing but the colors of the Rangers and were all skilled martial artists kept disappearing just before the Rangers showed up. At least Tommy, as the Green and White MMPR Rangers, the Red Zeo and Turbo Ranger, and the Black Dino Ranger, got to change his every so often.
- The current page image comes from Samurai Sentai Shinkenger, whose adaptation, Power Rangers Samurai, is currently airing (as of 2012.) Actually, they're... much less obsessively colorcoded than some series.
It's so expected that it's confusing when they don't. In Kamen Rider Dragon Knight, not all the Riders' unmorphed bikes are the same as their Rider colors, which makes it hard to tell who's who when they wear visored helmets. Power Rangers Operation Overdrive has the same problem with the bikes and ATVs used when unmorphed. We laugh at the heroes who seem to wear nothing but their colors, but it turns out Tropes Are Not Bad.