Pretty good, especially since it was the only handheld version of the game.
In Hyper Mode (1 Player), you select your character and the game selects 3 random characters from the list that play as your opponents. You compete in every sporting event in the game within a 2-day period (in game time, of course) and adds up your points at the end of day 2. The player with the most points total is declared the winner. Records for each sport will get recorded. You can view the records in Point Ranking. In Practice Mode (1 Player), you can practice any sporting event in the game. Results do not get recorded. In Story Mode (1 Player), your goal is to win the Olympics by training, leveling up your stats in running, jumping, throwing, and stamina, and mastering the sporting events in the game. The Story Mode also includes unexpected events, such as getting a girlfriend, getting a sprained ankle while training, etc. 2-Player Versus Mode basically says what it is right there. No need to explain it further. Point Ranking allows you to view personal records for each sporting event in the game; records only get recorded when playing in Hyper Mode.
I hope you enjoyed my review of International Track and Field for GameBoy Color and found it useful.