Light yellow, white, or transparent are considered as normal. If it is grey, green, or bubbly, with strong smell and/or with itchiness and burning sensation then you should consult your doctor to make sure everything is ok. It is very common to have virginal discharge and sometimes around our ovulation, the amount of the discharge/cervical fluid will increase. Nothing to worry about.
In fact it is better for us to wear cotton underwear and avoid using panty liner. A dry and clean environment is always better and can minimize the chance of getting any infection.