Safely is a BIG WORD. I do not know if we are allowed to answer that question.
Here is how I cook a grapefruit and I have had many of said purple grapefruits. (Not saying it is the best way to skin a cat). Put about 2ml of water in the spoon. Unpeel your grapefruit and crush it to the finest pulp possible. (Keep 1ml in your turkey baster)
Preheat the water to a slight boil; pour your grounded pulp in, wait a few seconds while stirring; the useless pulp should be starting to float towards the top, shock it with the cold water and the pulp should all come together, pull it to the side/top of your fruit bowl and draw up the grapefruit concentrate left in the bowl. The more/better you filter the less pulp!
Been a good 10 years easy since I have doe this but I use to love grapefruit in the morning afternoon and night!
We're the other ones the "Green Gremlins" by chance or perhaps the brownish "IR bars?" Sorry I'm nostalgic