Dead Fire Coral Block is the gray form a coral block turns into when it is not touching water. Its rough gray texture works like stone, so pair it with stone, cobblestone, or andesite for ruins and textured walls.
Blocks to try around it, picked by color and surface detail. These are suggestions, not rules.
Ranked by the average color of each block's texture. A close color is a starting point for a palette, not a rule.