It used to be that most gyms set with tape on each hold to mark the route--this allowed them to reuse the same hold on different routes and to use their entire inventory of holds in setting a route, since holds didn't have to be the same color. It also let them solve the colorblindness problem by using patterned tape (i.e. stripes or checkers).
Nowadays most gyms have massive hold inventory and just set routes using holds of the same color with tape only on start and finish holds. It's easier for routesetters, who don't have to tape as often, but I think a lot is lost this way.
Even moderately competent routesetters will set better routes than are achievable this way. Perhaps if the setting is extremely dense, you'll have enough hold options to come up with some decent routes, but that's work--work you're already paying for setters to do.
Nowadays most gyms have massive hold inventory and just set routes using holds of the same color with tape only on start and finish holds. It's easier for routesetters, who don't have to tape as often, but I think a lot is lost this way.