Remove the peel of the grapefruit, section it, and then take the skins off each section. If you are going to arrange this recipe beautifully on a plate, try not to break the sections.
Slice the avocado into thin, long slices.
Now you can either throw all the diced, sectioned, and sliced ingredients into a bowl and douse it with a high quality olive oil or arrange them beautifully on a plate and douse each individual plate with olive oil.
When you store it all together, the avocado won't get brown because of the acidic grapefruit juices.