If you feel the cold easily, it is recommended that you wear tights under your ski pants. This will ensure you stay comfortable, and, above all, warm! Depending on your sensitivity to the cold and the weather conditions, you can choose the thickness of the tights depending on how warm you want to be. This is the case for example with Ortovox and Icebreaker.
Ski tights come in different types: merino wool for maximum warmth and comfort, but also synthetic, such as X-Bionic or Odlo. Go for a 3/4 length to avoid them bunching up in your ski boots. Your base layer bottom must be relatively tight to retain maximum warmth. Snowleader has a large choice of technical base layer bottoms in plain colours (black, grey) or brighter colours for those who like colour!