The yellow colour in tomato is due to

The yellow colour of tomato is due to carotene.
Relative to phytonutrients, the most abundant in tomatoes are the carotenoids. Lycopene is the most prominent carotenoid followed by beta-carotene, gamma-carotene and phytoene as well as several minor carotenoids.
During ripening, the colour of the tomato turns from green to red. The carotenoid pigment lycopene produces this red colour. Lycopene is the red carotene that is synthesized as a result of the breakdown of chlorophyll.