Checking is a separation of the wood fibers along the grain. This occurs when wood is drying, as the fibers expand and contract and internal pressures build up. The checks in our material happened long ago, when the trees were cut down for their original purpose and the exterior dried faster than the core. We defect any material with checks the would present a structural issue.
Color variation should be expected on the materials that specify this characteristic. Either the product is crafted from several species or one species with a range of color from sapwood to heartwood to grain.