Grease and brakes are a no-no. I believe the tubes you are describing are a brake silencing membrane. The go on the outside of the pads prior to installing them in the calipers. Their purpose is to absorb the vibration that occurs when braking. This vibration causes the squeal that we are all familiar when we brake. Some pads come with little self-adhesive shims which are supposed to prevent squealing, also. Personally, they don't work very well for me, but it won't hurt to apply it on. After you apply it, let sit for about 10 to 15 minutes so that it hardens and isn't so tacky when your handling them. REMEMBER, NEVER APPLY GREASE OR ANYTHING ELSE ONTO THE BRAKE LINING ITSELF! Not sure why you have two different colored membranes with your brake pads. Maybe someone else knows.