It looks like the roots are dying.
The potting material is rather dense around the roots. The pot is also without any ventilation slits or holes.
This, combined with too much moisture, could be a cause of root rot.
BUT!
I believe you can save it before it goes any further.
Here's what I would do:
1 - Carefully remove the plant from the pot.
2 - Clean as much potting mix from the roots as possible without cracking or breaking any.
3 - Give the roots a good washing in room-temperature water
4 - Sterilize a pair of sharp! scissors with alcohol or flame and snip off any brown or shriveling roots up a bit into the green part. You don't want to leave any brown part on. If the whole root is shriveled and brown, cut it as close to the base of the plant as possible.
5 - Leave the plant bare-root in an empty pot for a couple of days. This will allow the wounded roots to seal up the cuts without more risk of infection. You can even dab the cut root tips in a fungicide.
6 - You can leave the plant out of pot for as long as you want, keeping in mind that the roots must be soaked once every day. This way you will ensure maximum air to the roots as well as give you the opportunity to inspect the roots for more rot.
7 - When you reach a point where you are fairly certain the roots have stopped rotting, give them a good soaking and repot the plant in a big, chunky potting medium, like 1 to 1.5 inch pieces of lava rock or fir bark. These big chunks of media will ensure lots of air circulates around your orchid's roots and greatly reduce the chance of more root rot.
I hope this is helpful.