I could use some advise on fishing crankbaits in waters 20 to 40 feet deep.What are some suggestions for clear water lakes as related to size and colors of bait ?

20 to 40 feet? I'd say throw a jig or drop shot, especially if the water is clear! If you are looking to cover water and get reaction strikes, research the "stroking" technique with heavy football jigs.

The only way a crank bait is going to reach 40 ft is by long lining on 8 or 10 lb test fluoro. That technique won a recent BASS tourney.

As far as favorite cranks for fishing the 20 ft mark: Strike King 6XD, Norman DD22, Bomber Fat Free Shad BDS8, and H2O Xpress, Rapala DT Metal 20. All will catch fish, as long as you much the hatch. Use fluoro between 8-12lb test, and make long casts. Don't be ashamed to use the old' kneel and reel technique. You should pull a few fish up!

Good luck!