Seen some yellowish discharge on underwear (towards front), had no other discomfort (no burning when urinating/ itching etc) is this abnormal?

Maybe not.: The color of the normal vaginal discharge can vary during the course of a menstrual cycle. Diet and medications can affect the color and smell. A yellow-tinged discharge is not uncommon & normal for some women. Infections can too, so if you have had unprotected sex, and an STD is a possibility, get checked. You can have an STD and have no pain or itching, just a change in mucus color/amount..