Yellow leaves on your Chinese money plant are often a sign of poor drainage/overwatering or receiving the incorrect amount of light for its needs.
SIGNS TO LOOK OUT FOR
Yellow leaves aren’t always a sign of poor plant health - if it’s only a few older leaves that turn yellow every now and then, it's actually just a sign that your Pilea is getting older.
New leaves will come eventually, so you can either let the old leaves fall off on their own or pluck them off if you find them to be unsightly.
However, if instead it's the new leaves of your Pilea that are turning yellow, it could mean that your Pilea is getting watered too much, which could, in turn, lead to further problems.
If you’re unsure whether the yellowing of the leaves is normal or if it’s a sign of overwatering, you should keep an eye on your plant’s overall health. Overwatering can be very harmful to a plant, so it’s likely that it will start showing other symptoms of damage. One quick way to check this is to feel your Pilea’s soil - if it stays wet for a prolonged time after watering, you should hold off watering until it has had the chance to dry out somewhat.
WHAT TO DO NOW
Avoid watering your Pilea again until you have made sure that the soil has dried up a bit more first.
Then, all you need to do is try to act preventatively to make sure this doesn’t happen again. Making sure that it is getting the right amount of light is also important, as Pilea peperomioides can be sensitive to too much light.
Check that your plant pot has sufficient drainage - try to make sure that it has holes in the bottom wherever possible, and never allow it to stand in water. You should always empty out any water that collects on the dish under your plant.
By doing each of those things, and having a bit of patience as you give your plant some time to recover, you should see that the leaves will start to regain their green colour.