This contrast is a bright orange color. You can use them to e.g. paint your Magmadroth or for orange-reddish hair (e.g. Fyreslayer)
Games Workshop Contrast Paints are designed to be applied over a large area over a light base such as White Scar, Corax White, Gray Seer or Wraitbone Spray. When the color has dried, the painting is often sufficient for tabletop standard requirements, with layer colors additional layers can be built up on the contrast color and more details and highlights can be extracted from the model.