what can be done to improve the look of the rusty master cyl. and discolored booster? thanks

You could remove, prep, and paint them. Eastwood specializes in offering paints for these purposes. There are likely other brands also.

For master cylinder:
http://www.eastwood.com/ew-brake-gray-aerosol-13-oz.html

For booster:
http://www.eastwood.com/new-golden-cad-system-w-diamond-clear.html

You could also send them out to really do it "proper." Just Google search "brake booster plating" and choose the vendor you like best. LOTS of companies perform this service.

I used Plasti-cote cast iron grey on the master cylinder and distribution block. Sanded the brake lines lightly to original and clear coated. The booster is mprobably a delco and should be the gold type plating. I didn't want to invest in that and decided to paint my booster satin black. Looks good but not totally original.

Eastwood makes a 3-part spray on cad plating look alike system. If done correctly on the booster and master lid it looks excellent IMO. You first spray the booster with the gold color, then hit the booster randomly with the green spray can, then again with the red spray can. It takes a bit of practice, but I will say if you take your time and have some patience, IMO it looks very good! And very close to actual real cad plating. I did the one in my 68 Bird when I first bought it and it looked good for many many years and people often complimented on how nice the "cad plating held up for so many years" from people who knew the car over a long time period...

I also believe Eastwood recently came out with a cast iron paint specifically for master cylinders that is more resistant to brake fluid.

I have always just loved the Eastwood paints. High solids, easy to spray and looks good and seems very durable.

For my master cylinder, I powdercoated mine. I did mine in black, but have done other peoples in cast iron color. The powder isn't affected by the brake fluid that will eventually end up on the body of the mastercylinder. Of course, if you do this, you need to remvoe the piston and the residual valve and flush the master out, but it is a nice long standing look.

i painted mine gold , then over spayed with green and red i think, it looks ok. So it looks like gold with tiny specks of green and red. from a distance it looks good.