Colin Farrell -- Good Genes or Good Docs?!

Colin Farrell's beauty will make you green with envy!

Here's a 23-year-old version of the Irish actor at a dinner in West Hollywood back in 2000 (left) and 19 years later ... the now 42-year-old "Dumbo" star was seen flaunting his golden good looks at the movie premiere in Los Angeles earlier this week (right).

Must be the luck of the Irish!

The question is ...