"I personally assume to get Color transparent when subtract two absolutely equal colors."
why ? that makes no sense to me. I guess we reason about things differently. In art black and white are not colors, they are called "neutrals" and they have the meaning of the existence of light (white) and non existence of light (black) as such black has the meaning of zero. Transparency does not affect colors its a characteristic of materials by allowing some of the light to pass through. In my view for arithmetical operation transparency should be ignored and operate only on the color itself.
