Well, actually, they aren't. The International Tennis Federation (ITF) categorizes the color as "optic yellow.” Incidentally, tennis balls actually used to be black or white. When tennis started to be televised in color in the late 1960s, it was hard for viewers to track the ball on their screens, so the ITF came up with the bright greenish-yellow to make it easier on their eyes.
They're rare today, but according to ITF rules, white tennis balls are technically still allowed—a relic of pre-TV times.
yellow i think
The majority of golf balls are white, but there are some yellow balls which are for evening play and are used by seniors. Paula Creamer sometimes uses a pink ball.
fabric
Bright yellow.
Green.
It does reflect light, as anything does that you can see (a yellow tennis ball reflects yellow light and absorbs the other colors). However, it will not show you your reflection.
the most visible ball in tennis is red yellow.
rubber and green fuzzies
Tennis balls are not generally yellow. They are usually green. A tennis ball can become yellow if it is left out in the sun for a very long time (months and months), and will turn yellow due to sun exposure.
Green.
I believe Rene LeCoste invented a hand-cranked machine that propelled tennis balls, while Bob McLure reversed the motor on a vacuum cleaner to create the first commercially viable ball machine in 1970.
I am thinking the anser is 5/8... hope it helps