glColorMaski

glColorMask: man3/glColorMask.xml

glColorMask and glColorMaski specify whether the individual color components in the frame buffer can or cannot be written. glColorMaski sets the mask for a specific draw buffer, whereas glColorMask sets the mask for all draw buffers. If red is GL_FALSE, for example, no change is made to the red component of any pixel in any of the color buffers, regardless of the drawing operation attempted. Changes to individual bits of components cannot be controlled. Rather, changes are either enabled or disabled for entire color components.