Quote - I have been too busy to come back and explain. It's very helpful that others chime in.

ice-boy: Do this simple experiment. 

Load any "color" image you want - anything at all - into the material room.

Attach a Component node as I described.

Examine the preview of the component node. It is not red or green or blue or any other color.

The red channel of an RGB color image does not have "red" stuff in it. It has numbers. These numbers indicate how much red to draw. Similarly the green channel does not have "green" stuff in it, nor the "blue" channel any blue stuff. These are just luminance values - gray-scale numbers.

When you examine one by itself, via the Component node, all will be revealed.

i have been using this for over a year. but not for bump and specular. but for masking. i created 3 different masks with blue,green and red colors. then with the Component node i seperated them. but i understand how it works since masks are black/white.  

but i still dont understand how i could use a bump and specular image together since with bump i am using black,grey and white .