In LÖVE 0.9.2 and below, love.graphics.setColor calls glColor itself, which will overwrite your glColor call. LÖVE also sets an orthographic projection matrix in the GL_PROJECTION matrix stack with a size equal to the window's size, so your triangle is probably showing up, just at a very small size...

Hello everyone i downloaded the file 'OpenGL.lua' from GitHub and i'm trying to use OpenGL in Love project just it's interesting. But 'glColor3f\i(r,g,b)' doesn't work i see the black triangle but 'glClearColor" works great maybe someone knows what is the problem. P.S sorry for my broken englis...