Complex sentence: The hachures are traditionally monocolour, usually black, gray or brown; using two complementary colours for the hachures on a neutral background colour (e.g. black and white lines on gray map colour) would give a shading effect as if the relief were illuminated.
Split into simpler sentences: The hachures are traditionally monocolour, usually black, gray or brown. Using two complementary colours for the hachures on a neutral background colour (e.g. black and white lines on gray map colour) would give a shading effect as if the relief were illuminated.