Softball is variation of baseball with a larger ball and smaller field.
For the teams playing in NCAA games, Rule 3 covers the ball. So much for the yellow ball simply being a preference.
a. The ball shall be an optic yellow sphere with raised red thread seams. It shall have a center core of polyurethane mixture, No. 1 quality long fiber kapok, or a mixture of cork and rubber. The cover shall be smooth and made of chrome tanned, top grain horsehide or cowhide. It shall be affixed to the core by cement and sewn with waxed cotton or linen thread by the two-needle method with not fewer than 88 stitches per cover. The ball shall meet the following specifications:
Minimum circumference: 11-7/8 inches
maximum circumference: 12-1/8 inches
Minimum weight: 6-1/4 ounces
maximum weight: 7 ounces
Maximum COR (coefficient of restitution): .47
Maximum compression: 350 ±50.
b. The home team shall be responsible for providing a minimum of five game softballs of the same specifications and manufacturer. Each game shall begin with two new game balls (one rubbed by each team, so the manufacturer’s gloss is removed) and three additional (new or game quality) balls.
c. The use of any treatment or device that fundamentally changes the specifications of balls is prohibited and renders the equipment altered and unsuitable for play.
Photo – kansan.com/sports/2013/03/06/kansas-focuses-on-success-rather-than-opponents/