Developers are obsessed with Lovecraft's 'cosmic horror' mythos at the moment, but only a few are heading straight to the source, making games based on actual Lovecraft stories (or, in this case, a game based on a pen-and-paper RPG based on an actual story). Styx developer Cyanide is the latest developer to make a game titled Call of Cthulhu, and this one's an "RPG-Investigation title, packed with psychological horror and stealth mechanics".
"Players will control Edward Pierce, a former veteran and private investigator in 1920s Boston. Pierce will be investigating the tragic and mysterious death of Sarah Hawkins and her family in Darkwater Island. The game’s E3 Trailer showcases this disturbing Island and the eerie Hawkins Family Mansion, and gives a glimpse at how the intensity of the investigation will slowly start chipping away at your Sanity."
You see how 'Sanity' has an uppercase S there? That means it's a game mechanic, something that's explained a bit further on in that YouTube trailer's descriptive text:
"Insanity and the Cthulhu Mythos have long been entwined – as your investigation brings you closer to Cthulhu’s sphere of influence, madness will progressively engulf your senses, leaving you to increasingly question what is real and what is illusory."
Don't expect any rainbows, basically, unless they're dread eldritch rainbows that incite madness in anyone who lays eyes on their unknowable hues. However, do expect Call of Cthulhu in 2017, which is when the game is scheduled to hit PC and consoles.
Here's that E3 trailer: