look at the answer of wallidmujahid to the comment of jjtfsalglado down for clarification, it is quite clear:

"Find the greatest difference in length for any possible pairing of strings between Array1 and Array2"

Do you know what is a enum?

If you don't know what is it, perhaps you should go look it up ;-)

Color is a enum, so...

Some clarification would be needed about distinct colors. What makes a color a distinct? As far as I found on google it is quite subjective since it depends on a person's perception?

So what features of a color have to be searched to find it distinct?

I don't really get the point of this kata...
It is a 8kyu, ie very basic kata.
Shouldn't be the best practice for very beginners to create classes with getters and setters? (at least in java)
Is it a better practice to create attributes by method chaining inside a getter method than using setter method? (This is a real question which I don't know, since I'm still learning Java from the basics)
If so, than I suggest to state in the description that "You have to provide a random selection of colors inside the class that will be accessed when the object is referenced."

Fixed, please try again.

The tests are not runnin at all:

"Failed to detect class name:
// Insert smiley face;"

The negative sign is not a digit, it is just a sign, therefore it shouldn't make a number to win

It doesn't count. The Test6 won't fail without considering the negative sign either. The instruction says "If two numbers in the argument array have the same number of digits, return the first one ..." In Test6 that is the case.

what to do if "It took longer than 20000ms to complete" error message received? what kind of optimization should i do?

read this, it helped me a lot to understand the NPE and it also contains the way how to get past it:

https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it

My question is if Lists contain objects not primitives then how is it possible to make operations with them like multiply and raise to power, etc? I just tried by expecting it won't work anyway, but it did.