why were the wooden top masts of early sailing yachts almost always painted white?

Here's some speculation on the subject of white topmasts:

"1) on gaff rigged boats of old the masts were oiled or greased (often
tallow) to prevent the wood from drying and to reduce friction/wear
from the gaff saddle or jaws. When paints and varnishes became more
widespread the earlier ones were not capable of coping with the wear
of the gaff jaws so in order to reduce maintenance the masts were
painted above the highest gaff jaw wear-mark or on the topmast for the
same reason. Lighter colour paints proved better at reflecting the
heat/drying of the sun so it evolved that the top sections/topmasts
got painted white. When bermudian rig came along, even though there
was no gaff jaws to wear the mast, the 'fashion' of white top sections
continued for no real reason.

2) with the advent of the marconi mast (no topmast) the top section of
the mast was tapered. This tapering, if prominent, tends to reveal
endgrain along its length and as endgrain is more vulnerable to
moisture ingress/egress it needed good protection and light colour
paint did a better and less maintenance dependent job than varnish."

http://www.ybw.com/forums/showflat.php?Number=618887

Pink's comment answers the question's "why".

Hello Pinky,
Please note that the answer here has been removed ...
regards, myo