An instance is a RGB color value.
Constructor: creates a new RGB value (r,g,b,a).
param r: initial red value param g: initial green value param b: initial blue value param a: initial alpha value (default 255)
The alpha channel is 255 by default, unless otherwise specified.
Precondition: r, g, b, a must all be ints between 0 and 255, inclusive
The red channel.
Invariant: Value must be an int between 0 and 255, inclusive.
The green channel.
Invariant: Value must be an int between 0 and 255, inclusive.
The blue channel.
Invariant: Value must be an int between 0 and 255, inclusive.
The alpha channel.
Used for transparency effects (but not in this course).
Invariant: Value must be an int between 0 and 255, inclusive.