patch 8.2.3562: cannot add color names

Problem:    Cannot add color names.
Solution:   Add the v:colornames dictionary. (Drew Vogel, closes #8761)

src/gui.c

@@ -4785,7 +4785,7 @@ gui_get_color(char_u *name)
 	    && gui.in_use
 #endif
 	    )
-	semsg(_(e_alloc_color), name);
+	semsg(_(e_cannot_allocate_color_str), name);
     return t;
 }