There is a lot to take in account. There is a very fine balance in making it both visible and ledge-able on a crazy open and difficult surface. What will work are bold angular and/or curved lines, basically anything that breaks up the vertical and horizontal nature of the surface. As you have seen above the black is the most ledge-able due to contrast, while the horizontal line of the last "h" gets lost on the silver just because it follows the horizontal bar of the IC. It is also tough to judge it from one picture. If there was better lighting and a more straight on shot it might be more visible.