Yellow drainage is a sign worth knowing about.
With surgical wounds, contact your surgeon if the drainage coming from or around the incision increases or becomes thick, tan, green, or yellow, or smells bad. That combination is pus.
With an ischemic ulcer, more drainage than before, or drainage that is yellowish or cloudy, is one of the signs of infection to contact a provider about. With a diabetic foot ulcer, extra drainage and pus are each signs on their own.
In general, pus or a change in the wound fluid is one of the signs that may suggest infection.
Keep one thing in mind so this doesn’t become alarming in every case: not all wounds with fluid or smell are infected, but changes over time are important.
One more thing is worth separating out, because the same color word comes up in a different setting. Pressure sores covered in dead skin that is yellow, tan, green, or brown are called unstageable. That is tissue in the wound bed, not fluid coming out of it. They are different findings, and the color alone doesn’t tell you which you are looking at.