Light green leaves for cattleyas
 

I grew cattleyas outside in summer and kept under tree. Some get sunshine in the morning and some in the afternoon. I found it is easy to get light green leaves for cattleyas with white or yellow flowers. However, it is impossible for me to get light green leaves for purple, red or green flower cattleyas. I still have flowers for most of them every year. Did I do anything wrong?

I doubt you did anything wrong. I find for some of my pink, purple or red Catts, that rather than get paler green, they can get dark and have some purple colouring on them. Several of mine on new growths had almost solid purple on the backs of leaves. So long as they are getting good light and are healthy and if they bloom, then all should be well.