BURNT LEAVES: When your Pothos gets too much sunlight, it'll get sunburns on its leaves. The sunburns will show up on the variegated parts of the leaves most of the time and are unfortunately permanent. Sunburns won't heal, so you could trim the leaf off if you want to.
YELLOW LEAVES: When you see your Pothos' leaves to yellow, it's most likely due to incorrect moisture levels in the soil. Especially overwatering your Pothos will cause the leaves to turn yellow. However, if you're consistently water your plant too much and let it dry out for too long, it will also stress out your Pothos. In this case the leaves will also turn yellow.
BROWN SPOTS: When your Pothos is not exposed to direct sunlight, but it's still getting brown spots it could be due to overwatering. When your Pothos is suffering from root rot, the variegation often turns brown. So if you're sure you're not giving your Pothos too much sunlight, it's good to have a second look at how much water you're giving it.