--- src/include/libgrx.h.orig	2007-03-08 20:28:00 +0000
+++ src/include/libgrx.h	2008-05-15 10:02:14 +0000
@@ -295,11 +295,11 @@
 int _GrResetColors(void);      /* like GrResetColors but return true on success */
 
 #ifdef __TURBOC__
-#  define C_OPER(color)   (unsigned int)(((unsigned char *)(&(color)))[3])
+#  define C_OPER(color)   (unsigned int)(((unsigned char *)(&(color)))[3] & 15)
 #endif
 
 #ifndef C_OPER
-#define C_OPER(color)   (unsigned int)((GrColor)(color) >> 24)
+#define C_OPER(color)   (unsigned int)(((GrColor)(color) >> 24) & 15)
 #endif
 #define C_WRITE         (int)(GrWRITE >> 24)
 #define C_XOR           (int)(GrXOR   >> 24)