How can I get the color of a point rendered using SDL_SetRenderDrawColor and SDL_RenderDrawLine

SDL_SetRenderDrawColor(renderer, 255, 0, 0, 255);
SDL_RenderDrawPoint(renderer, (window_height / 2) + xxi[i], -yyi[i] + (window_width / 2));

This is my code.
Now I wanna get the color of the xxi[i] and yyi[i] pixel.
But I don’t know how to.

SDL_RenderReadPixels() will do that, but it can be very slow so is only suitable when that doesn’t matter.