Thanks to youtube, you can see how Technicolor went from its two-strip to three-strip format.
Toll of the Sea (1922) - first full length 2 strip technicolor film (complete film) - the final shot was re-created for the film's restoration
Phantom of the Opera (1925) - 2 strip Technicolor sequence. If you chance upon the restored versions, note the changes on the hallway walls as it cuts from the color to black and white shots. This film had some insane production challenges...
La Cucaracha (1934) - first theatrical release in 3 strip technicolor - 2 reeler
Becky Sharp (1935) - first full length 3 strip Technicolor film (restoration promotion):