Red Coloring in Mee Goreng etc. ミーゴレン等

Indian Muslim stalls in Singapore's are very unique, meaning, most of the food are not found in India and it's something very very unique to Singapore. Mee Goreng (Indian style fried noodle), Sup Tulang (bone marrow soup), mutton steak (sauteed chopped mutton with spices), mee kuah (egg noodle with starched mutton gravy) and the list goes on. What I noticed not recently but from long time ago is that, Indian muslim (mamak) chefs love using red coloring. Some may argue that the red coloring comes from spices but I doubt it. Something so brightly red cannot depend solely on chilli powder. Red color is a special thing for Indians; take a look at those Tandoor chickens with bright red coloring. I asked my Indian friend why the red color. Is it a lucky color or do they add it to make it more delicious (which does not impress a Japanese like me). He couldn't answer so I guess a lot of people take this "red coloring" as a given already. I read somewhere that "red" excites tastes buds in Indian culture. Persian version (which current North Indian cuisine got its most influence from during Mughal rule) of tandoor chickens is not red though. They are simply marinated in yogurt with few other ingredients. But with all these red colors in mee goreng, mee kuah, sup tulang, etc. why is it that sup kambing is not red? I wonder why.