Why are new leaves mainly reddish in color?

Question

I was wondering why are new leaves sometimes red?

Answer 1

Reddening of leaves is a defence mechanism. The young emerging leaves sometimes ( particularly when the environment is cold or there is intense sunlight) need protection for continued unhindered growth. The development of anthocyanin pigments which imparts the red colour precisely do this.
Sometimes you may see that in autum even older leaves ( particularly whem the temperature is very low), the reddening effect is seen. I am reproducing here how the protection is given to the leaves by anthocyanins.

Anthocyanins provide the red special effects for much of the plant kingdom. Their fireworks intrigued 19th-century biologists, who discussed the possibility that a leaf might make anthocyanins during a period of vulnerability, to shield the green chlorophyll pigments from sunburn.
This probably helps in the screening of especially vulnerable leaves—the extremely young and the extremely old—from ultraviolet (UV) radiation.
It has been postulated that when the leaves are exposed to intense there is overloading on the light-gathering chlorophyll and and actually slow it down, a misfortune called photoinhibition. All-green leaves ( particularly the younger immature ones) seem to suffer greater photoinhibition than do two-tone ones of the same species. A plant with a little protection in the form of anthocyanins could off-load some of that sudden excess energy in the form of its chlorophyll and better withstand a blast.
In a color-changing leaf, the plant's metabolic pathways for making the initial capture of energy don't lose their efficiency as fast as the subsequent pathways for processing that energy do, a risky imbalance that invites overloads. Seasonal stresses, such as chilling temperatures, also hobble the leaf metabolism.
The evidence suggest nicely for anthocyanins as safety measures against light overdose
There are other functions of anthocyanin too. The antioxidizing powers of the leaf anthocyanins has been recently indicated which is very important for the young growing leaves.
A suggestion for yet a third function for anthocyanins in leaves comes from physiologist Linda Chalker-Scott of the University of Washington in Seattle. She proposes that the pigments regulate water movement. Anthocyanins dissolve in water, whereas chlorophyll and a lot of other cell pigments don't, she explains. Water loaded with any dissolved substance has what physiologists call lower osmotic potential, a decreased tendency to flow away. Loading water with dissolved substances also lowers the temperature at which water freezes, potentially an advantage on a frosty fall night.
Plenty of other ideas for anthocyanins' function also remain to be tested. Observers of fungus-farming ants, for example, reported in the 1970s that the ants avoid taking red leaves home to feed to their garden. Researchers have speculated that anthocyanins might discourage growth of some fungi.
Another hypothesis states that anthocyanins keep leaves from overheating; an alternative has the pigments protecting leaves from cold.

Answer 2

To be honest, I have never seen this. The buds are always green and the new leaves are green. Sorry.

Answer 3

More of xanthophylls and less of chlorophyll.