The quality of the King Kong Colorized is quite good for Laserdisc, though it will never be quite as good as archival material on black and white in High Definition on a Blu-Ray.
Captain Blood was only released once Colorized on VHS. I tried to find the Laserdisc it doesn’t exist.
As for Casablanca i never heard that was on Laserdisc, i know someone taped it and wouldn’t share his copy. He also had Citizen Kane, the Sea Hawk. Treasure of the Sierra Madre etc.