In a dry skillet over medium heat, toast coconut flakes for 1 to 2 minutes, stirring frequently until golden and fragrant. Set aside.
In a large bowl, combine the cucumber and jicama. Gently fold in the grapefruit segments. Season with salt and, if desired, chili powder.
Drizzle with vinaigrette just before serving and toss gently. Garnish with toasted coconut and micro cilantro.