Here's my guesses for the icons:
Some are obvious...
orange star badge = police station
blue tennis racket = tennis courts
blue golf flag = golf course
green shirt = clothing store
green scissors = barbershop
green spray can = car shop
green heart = tattoo shop
green gun = AmmuNation
Some aren't quite as clear, but might be safe to assume...
orange six-point badge = hospitals
blue crosshairs = firing range
blue "indian sitter" = yoga
pink heel = strip club
pink camera = movie theatre
Some are very much up in the air...
Blue "pc" = possibly Publicly traded Companies to invest in...badge is by the rock quarry, wind farm, airport, among many others
black airplane = private airstrip?
orange car with ??? above it = taxi depots?
blue parachute = obviously something to do with jumping out of a plane, but why would they have these all over the city?
purple binoculars =
purple mountain =
purple house with $ = some form of property? seems like way too many to be safehouses...and why wouldn't there be one in Chumash if they were homes for purchase?
To me it seems that orange indicates it's a public good (cops, health service, transportation); green are things to customize your character (hair, clothes, tats, car, guns); blue are activities (golf, yoga, exercise, tennis, parachuting, playing the stock market); pink are more related to leisure like watching a movie or making it rain; purple confuses the sh*t out of me in general...no idea how these could be related.