Colors do effect human emotions, irregardless of whether we individually prefer one over another. In the realm of color psychology, orange is a combination of joy and passion, and functions as a stimulant. Research shows the color orange actually increases the supply of oxygen sent to the brain.
An orange & gray checkered Neyland would look cool--in the "never seen that before" way. But the emotional mood it creates would be somber.
Psychologically, gray actually inspires passivity. It de-motivates people and decreases energy levels.
Orange & white are a high contrast combination, creating vibrancy. Orange & gray are low contrast, creating a mood that is calming and sedate.
I personally like orange and gray together, but maybe that's because the work week is usually stressful, and my brain is ready to relax over the weekend (like I'm gonna relax with Florida coming)!
The best way for Vol fans to truly UTILIZE color like a band of color-psych guerilla ninjas would be to wear gray to away games. Be a downer on the road and dull the effect of our opponent's home crowd colors.