Most Mahogany found used on any instruments has been stained, darkening the appearance and highlighting the grain patterns. Mahogany is also pretty unstained, especially the local Hawaiian Mahogany. The most prized, revered woods of Hawaii, and now throughout the world. In Honolulu, beautiful architecture, carvings, and furniture made of Koa can be found as a legacy of Hawaii's mass deforestation of the 1800's. Even today, Koa is still the preferred wood, and in this case, for musical instruments.
Most trees have a characteristic, predictable pattern,hardness, density, and flexibility.
Not so with Koa. Almost every tree, and planks from each tree look different, being yellow, red, black, purple, green, and grain is either straight, curly, mottled, or quilted. Due to inconsistent hardness, density, and flexibility, the predictability of the sound of the instrument is difficult to determine. In most cases, the tone sounds good, similar to Mahogany, though usually more bright and trebly. Sometimes when the entire instrument is made of Koa, with the right density and flexibility, it sounds great.