I have ended up three different Bourbon varieties as beans; yellow, orange and red. Are they the same variety, just cultivated in different times of the maturity of the coffee cherries? Or, are they three separate varieties with separate cherry color when they are mature?
They are different varieties (at least 2 of them, red & yellow)
The original Bourbon was the Red. Founded in the Bourbon Island (now Réunion) near by 1790 aprox at carried it by the French to Africa and America (Brazil).
Then, in 1930, a natural mutation of the (Red) Bourbon was found at Sao Paulo (Brazil). This one:
The Orange, it's just another mutation. But I'm certain that is not a ripeness matter, it's a mutation/evolution thing.