Here’s a quick reference for grapefruit varities:
Duncan: lots of seeds, white flesh with great flavor; excellent for juicing; perhaps the oldest variety.
Flame: nearly seedless with red flesh and a slight rind blush.
Marsh (Marsh Seedless): nearly seedless, white-fleshed, medium-size with smooth yellow skin; it’s very juicy, tender and aromatic. You’ll find a balance of acidity and sweetness but somewhat less flavor than seeded varieties. This is a reliable old cultivar that’s great for juicing.
Redblush (also called Ruby Red and Ruby): seedless, pale-pink fleshed, and a yellow skin tinged with red. Red flesh fades to pink, then buff by end of season.
Rio Red: seedless, distinctly reddish skin and deep red flesh; firmer and smoother than Redblush; sweet-tart taste; excellent for juicing.
Star Ruby: seedless with the reddest flesh; clean and crisp tasting; easy-to-peel skin; smaller and less acidic than other varieties.
Melogold: grapefruit-pommelo hybrid developed in California; seedless with a sweet-tart flavor; bigger, heavier and thinner skinned than the Oroblanco; needs less heat than the true grapefruit.
Oroblanco: fruit is smaller, lighter and thicker skinned than Melogold; sweeter than Melogold; seedless with white flesh.