Okay, fine. I'm going to try and be a thorough as I can here, then I'm out.
When a person experiences something that triggers an emotion, a particular area of the brain becomes active (what part depends on the emotion.)
Using an MRI we can watch this activity in the brain and thus, we know which part of the brain controls which emotions. Using electrical stimulation we can then trigger these same emotions without outside stimuli (other than the electricity)
Now, on an MRI, the electrical activity associated with certain emotions appears in false colour. Sometimes it appears red, other times blue, it varies. The actual electrical activity going on in the brain has no colour (that I'm aware of).
Emotions like sadness, or in my case right now frustration, are simply the result of the brain's electrical activity. They do not exist outside the brain. They have no mass, no colour, and no size.
Again, it's a false colour image...