It's generally accepted among online lego communities that organizing by part/shape makes retrieval more efficient than organizing by color. It's tough to find a red 1x2 plate in a huge bin of red pieces, but it's easy to find a red 1x2 plate in a bin of small plates of multiple colors. If you don't have enough parts to justify breaking down to the specific part, you can do categories at whatever level of granularity makes sense for your collection: bricks, plates, modified bricks, rods and clips, etc.