There are a lot of aspects to achieving a consistent but natural looking stain finish. Different species and even cuts of woods have different qualities to their grain, different colors, and varying levels of hardness and absorption. Therefore, you should match your selected stain color with sample pieces matched to control samples provided for each species and cut of wood used, and have said samples compared and approved by the owner, designer, or architect. In addition, during the process of staining, the painter needs to use the approved stain product with the proper amount of material and proper technique to match the approved sample. It may be necessary to apply more stain in spots where stainable wood putty has been used, or in areas where the wood has varying levels of porosity and the color is too blotchy. Sometimes mixing in some stain into the base coat of sealer helps with finish color consistency. At any rate, since the beauty of wood is in its natural variations of knots and grain, it is up to the owner, designer or architect to determine what look is desired in the sample approval stage.