My understanding is that an RGB value with alpha value example could be this 0xffhexcode.
However, what I cannot understand is how 0xff0000ff, a solid blue with max alpha value, is an integer value greater than Integer.MAX_VALUE. How does the underline encoding in Java allow this to happen?
This is an interesting question which boils down to the definition of integer literals. For a full reference see the language specs at https://docs.oracle.com/javase/specs/jls/se9/html/jls-3.html#jls-3.10.1
The crux of the matter is that for an integer literal expressed in decimals, you can only represent positive integers. With a hex literal you can express positive and negative values. And specifically the value will be negative if the first bit is on.
To quote the language specs:
A decimal numeral is either the single ASCII digit 0, representing the integer zero, or consists of an ASCII digit from 1 to 9 optionally followed by one or more ASCII digits from 0 to 9 interspersed with underscores, representing a positive integer.
A hexadecimal numeral consists of the leading ASCII characters 0x or 0X followed by one or more ASCII hexadecimal digits interspersed with underscores, and can represent a positive, zero, or negative integer.
So to be precise 0xffffffff is not actually greater than Integer.MAX_VALUE because it is negative (due to the leading bit being on). Too add to the things that don't look right at first glance you can try:
System.out.println(Integer.MAX_VALUE == 0x7fffffff);
System.out.println(Integer.MIN_VALUE == 0x80000000);
Which will output true for both lines.