set_color
void(*set_color)(struct vc_data *vc, const struct rgb *c))
set_color(vc, &c);
set_color(par, regno, red, green, blue);
.set_color = annotate_browser__set_color,
.set_color = FILE__set_color,
int (*obj__set_color)(void *obj, int color) = wops->set_color;
int (*set_color)(void *obj, int color);