Several graphics context attributes can be modified at once using the changeGC:values: message. The following example creates a GC with default attributes, then changes the foreground and background colors.
| gc | gc := CgWindow default createGC: None values: nil. gc changeGC: GCForeground | GCBackground values: (CgGCValues new foreground: CgWindow default blackPixel; background: CgWindow default whitePixel).