Is "int2rgb" an OK method name?
As far as naming is concerned: Using 2 instead of to is pretty much a no-no - "to" is spelled out everywhere in the Java standard library. Further Java's naming convention is to capitalize every word, but the first in method names - except for acronyms which are all-caps no matter where they appear in the name. So the methods should be called intToRGB and RGBtoInt (to is lower case because it directly follows an acronym - compare for example Color.RGBtoHSB in the java standard library).

In regards to the code: I'd recommend representing your colors as Color objects rather than 3-element arrays. If you choose to do that, you don't have to define any of your methods, because that functionality already exists in the Color class.