glClearColor - specify clear values for the color buffers

glClearColor
	glClearColor(red, green, blue, alpha) -> None

void glClearColor( GLclampf red,
                   GLclampf green,
                   GLclampf blue,
                   GLclampf alpha )

red, green, blue, alpha
                      Specify	the red, green,	blue, and
                      alpha values used when the color
                      buffers	are cleared.  The initial
                      values are all 0.

glClearColor specifies the red, green, blue, and alpha
values used by glClear to clear the color buffers.  Values
specified by glClearColor are	clamped	to the range [0,1].

GL_INVALID_OPERATION is generated if glClearColor is
executed between the execution of glBegin and	the
corresponding	execution of glEnd.

glGet	with argument GL_COLOR_CLEAR_VALUE

glClear