Cara Cara oranges are a little sweeter than naval oranges and have a gorgeous deep pink color. They're fairly common, but if you can't find them blood oranges, naval oranges, or tangerines would make a lovely substitute. This salad is a perfect side dish as it is, but can be served over spring mix if you're looking for something more substantial.
Cut the grapefruit and orange in half crosswise (not through the stem ends), then slice into thin rounds. Use a paring knife to carefully trim away the peel. Arrange on a serving platter. Peel and slice the avocado; arrange over the fruit.
In a small bowl, whisk together the lime juice and olive oil. If your fruit is bitter, whisk in the honey to taste.