Need help on engine coolant check

[Nahid]

I am not a car expert so pardon my novice question. I want to properly check engine coolant (locally called radiator water here in Bangladesh). A local mechanic is telling me that my car needs to be added engine coolant. I have checked the user manual and it suggests that I need to check engine coolant reservoir to check if it needs more fluid. On the whitish reservoir box the pink fluid is above 'full' mark but if I open the radiator cap than the pink fluid is not visible. Should I top up engine coolant?