The Dark Stucco Wall is a dark red building-block. It can be crafted in your Crafting Menu (default key "Q") or at Crafting Tables (that still exist in worlds created before R22 on September 16th 2015), but only after the recipe has been unlocked upon taking/crafting a Stucco Wall for the first time (which is unlocked by taking/mining caramel-brown Canyonstone, found high up in Canyons-biomes), which will need at least a Stone Mining Cell to be mined. By crafting/taking a Dark Stucco Wall for the first time, the recipes for Dark Stucco Windows, Tin Walls and Tin Roofs will be unlocked.