Question: Why are there different color balls in racquetball?
About the article "Racquetball", section "Ball Colors".

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Bowling balls vary, depending on the type of bowling game.
Ten-pin balls are large, up to 27 inches in circumference (approximately 8.59 inches diameter), and have as many as twelve holes, typically three holes.
The balls come in various weights from 6 to 16 lbs, with the size and spacing of the finger holes often smaller on lighter balls to accommodate smaller hands.
Different kinds of balls are available for different styles of bowling.
There are balls for hook shots and balls for bowling straight.
The bowling balls meant for hook shots have different core shapes and different chemical covers.
There are a few types of chemical covers that allow a bowling ball to hook more.
One of these types of covers is a resin cover.
This resin cover is designed to move and absorb the oil on the lane to create a path for the bowler where there is less oil, increasing the amount of hook of the bowling ball.
Balls for other games vary, e.g., candlepin balls which fit in the palm of the hand need no holes.
Unlike most sports, the ball can be different weights based upon the player.
All bowling centers provide bowling balls (house balls) - their usage is included in the bowling fee.
For ten pin bowling, the center will provide a fleet of house balls in varying weight and standard grip sizes while idle lanes have empty ball return racks.
Customers that use house balls will pick a ball that fits from the house ball fleet and place it on the ball rack at the designated lane.
When done, the customer should return the house ball to the house ball racks.
In small-ball games, each ball return contains a quantity of house balls — usually in at most one or two color patterns. 
The International Racquetball Federation (IRF) governs the World Racquetball Championships, which were first held in 1981 in conjunction with the first World Games.
The second World Championships were played in 1984, and since then have been held biennially in August.
Players from the United States have won the most World Championship titles.
The IRF also runs the World Junior Racquetball Championships that occur annually in December, as well as the annual World Senior Racquetball Championships for players who are 35 years of age or older.
Racquetball has been included in the World Games on five occasions: 1981, 1989, 1993 and 2009.
Racquetball has been included in the Pan American Games in 1995, 1999, 2003, and 2011.
Toronto will host the 2015 Pan American Games, and they plan to have racquetball on the program.
There are three professional racquetball organizations.
The International Racquetball Tour (IRT) is the men's professional organization.
IRT tournaments occur usually in the USA, with some events occurring in Mexico and Canada.
The Women's Professional Racquetball Organization (WPRO) is the women's professional organization, while the Classic Pro Racquetball Tour (CPRT) is for players 40 and older many of whom were pro players at younger ages. 
Classification systems for disability sport were designed to allow fair levels of competition for competitors with different types of disability, with the sport utilising a medical classification system.
Competitors with ambulatory disabilities are able to compete against their able-bodied counterparts as a result of classification.
Internationally and in Canada, there is one classification eligible for participation: wheelchair users.
They must have a permanent disability that requires them to use a wheelchair, and may not be able to compete using rules for able-bodied players because of their disability.
In Canada, there have been different classes of competition inside wheelchair racquetball, with A and B at the 1989 Canadian Racquetball Championships.
For racquetball in the United States, wheelchair and vision impairment racquetball are both recognised with their own classification.
For players with vision impairments, three classes exist: B1, B2 and B3.
B1 allows for competitors who are totally blind or having some light perception, while B2 allows for competitors with vision range that allows them to recognise hand movement to 20/600 corrected, and B3 allows for competitors with vision impairments from 20/600 to 20/200 corrected.
Deaf racquetball has also been organised in the United States, with players being eligible if their hearing loss is 55 db or greater and sorted into divisions based on ability, age and gender. 
Disability racquetball classification is the medical based classification system developed to allow fair competition between racquetball players with different disability types and against able-bodied competitors.
Internationally and in Canada, this classification system only allows only wheelchair users to be eligible to compete.
In contrast, the United States classification system covers wheelchair users and people with vision impairments, with different classes inside these disability types.
Internationally, the sport is governed by the International Racquetball Federation, with national governing bodies also dealing with classification including the United States Racquetball Association and Racquetball Canada.
Rules for the sport were developed by the 1980s, and integration with the able-bodied side occurred by 1990 when able-bodied and wheelchair competitors competed in the same world championships.
Inclusion was challenged in a court in United States in 1995.
While the sport was never a full Paralympic one, it was a demonstration sport at the 1996 Summer Paralympics.
Classification is handled by the IRF Committee for Athletes with Disabilities who have the ability to screen or rescreen competitors for inclusion in the classification at their discretion.
There are rule modifications that differ for wheelchair users and vision impaired users. 
The European Racquetball Championships are organized every two years by the European Racquetball Federation (ERF), since 1981, to determine the strongest national racquetball teams and individual male and female players in Europe.