Update velocity/acceleration in PhetColorScheme and add momentum

[arouinfar]

Discussion started in phetsims/collision-lab#148

The colors used for velocity and acceleration in PhetColorScheme are holdovers from Java and we have been using different colors in HTML5.

Currently, the colors in PhetColorScheme are:
ACCELERATION: rgb( 0, 255, 0 )
VELOCITY: rgb( 255, 85, 0 ) (RED_COLORBLIND)

The colors commonly used in HTML5 are green for velocity and yellow for acceleration, though there have been some variances.

Sim	Velocity	Acceleration
collision-lab	rgb( 0, 255, 0 )	N/A
gravity-and-orbits	rgb( 255, 85, 0 ) (RED_COLORBLIND)	N/A
masses-and-springs	rgb( 41, 253, 46 )	rgb( 255, 253, 56 )
pendulum-lab	rgb( 41, 253, 46 )	rgb( 255, 253, 56 )
projectile-motion	rgb( 50, 255, 50 )	rgb( 255, 255, 50 )

I'd prefer to use the colors from projectile-motion for PhetColorScheme.VELOCITY and PhetColorScheme.ACCELERATION.

Collision Lab additionally has a vector representation for momentum rgb( 50, 50, 255 ). Momentum could appear in other PhET sims, so it would be good to add this color to PhetColorScheme.

@ariel-phet asked @brandonLi8 to make these changes to PhetColorScheme, so assigning to him. Once the changes have been made, please reassign to me so I can open issues in the relevant sim repos to update the colors.

[jonathanolson]

Applied in common code and collision-lab. @arouinfar back to you!

[arouinfar]

Thanks @jonathanolson, looks good. I've created issues in the sim repos for the outstanding work, so I think we can go ahead and close this one.