i was poking around on the internet just now & found this article from Kent Kobayashi from University of Hawaii at Manoa. It says :

"In correct light, some orchid plants will produce a pigment that resemble plum colored freckles or suntan. This is an almost ideal situation for good blooming."

source: ORCHID CARE--Kent Kobayashi

i think this is what has occurred, because the color change has happened only on the part of the leaves that are exposed to the sun. you can see in the 5th pic down that on the part of the bottom leaf covered by the top leaf, it has remained light green. like a sun tan almost.
anyhow, i will continue to monitor this phal for good measure.

Did you repost her recently? My phal did this once and it turned out she went into shock. She only had one root left when I finally found out. That was 2 years ago and she now has blooms that just opened today. I say you should Check the roots!

Hello.
All my phals have the same exact dark green color as shown on your pictures. They still grow leaves and many roots shoot out so I've been trying not to worry about it. But the phals on some of the popular orchid grower youtubers have bright green leaves and they are all very shiny! How?? Mines have completely matte / dull / flat dark green color.

Is this genetic? or Do they need even more lights??

Most of my phals are large in size (1.5+ feet one end of leaf tip to the opposite leaf tip). All my orchids are grown indoor in 100% sphagnum moss in Terra Cotta pots. They are under 20W AeroGarden Grow Light. 10 Inch or so distant from the lights. The LED light is very bright in eyes. The humidity in my home is 55% in Summer and 20% in Winter. So I have to water them more frequently in the winters. Nonetheless, I lose a lot of air roots to dry air. The home temp. is between 73F - 83F throughout the year. I have no fans for air circulation.

Any pointers to make my orchid leaves bright green?

Check out post #10 in this thread. Maybe lower your light a bit.

Dark Green Leaves
 

Thank you. Did you have the similar experience, by any chance? Were you able to turn the dark green leaves into light green?

First, Welcome

Don't get hung up on the leaf color. A Phal with a dark flower will also have some anthocyanin in the leaves, making them look darker than one that doesn't have so much, under exactly the same conditions. You need to look at the overall health of the plant - nice firm leaves. Phals are low-light plants, but they need sufficient light duration. So ideal is a soft light for 12 hours a day. If a Phal grows well but doesn't bloom, I'd look at increasing the light duration, rather than intensity, up to 12 hours. More than that is not likely to be useful. If you're growing by a window (rather than under lights you may need supplemental lights to get that increase in "day length"

Do note that this is a very old thread. Generally, it is best to start a new one to get noticed. Or join a more recent one - on this thread, the original poster and those who responded in 2013 and 2015 aren't active on the Board any more.

Some Phals have very light green leaves. Some have dark green leaves. Some have purplish leaves. In general they stay that way. If you want light green leaves you need to find that kind of plant.