修改CAD背景颜色

(defun c:bys (/ prefdisplay color)
        (vl-load-com)
        (setq prefdisplay (vla-get-display (vla-get-preferences        (vlax-get-acad-object))))
        (setq color (vlax-variant-value (vlax-variant-change-type(vla-get-graphicswinmodelbackgrndcolor prefdisplay)vlax-vblong)))
        (vla-put-graphicswinmodelbackgrndcolor prefdisplay (vlax-make-variant (if (= color 0) 16777215 0) vlax-vblong))
          (vla-Put-ModelCrosshairColor prefdisplay (vlax-make-variant (if (/= color 0) 16777215 0) vlax-vblong))
        (princ)
)