Flesh is still yellow. Taste is mild but pleasant according to wikipedia
The original 'Irwin' tree was a seedling of the 'Lippens' cultivar that was open-cross pollinated with 'Haden', planted on the property of F.D. Irwin in Miami, Florida in 1939. The tree first bore fruit in 1945 and was named and described in 1949. The fruit gained commercial acceptance due to its good production, flavor, relative disease resistance, and attractive color. 'Irwin' has also been sold as a nursery stock tree for home growing in Florida.
Today 'Irwin' is grown on some commercial scale in a number of countries, including Japan, Taiwan, and Australia, where it was introduced in the 1970s.
'Irwin' trees are planted in the collections of the USDA's germplasm repository in Miami, the University of Florida's Tropical Research and Education Center in Homestead, Florida, and the Miami-Dade Fruit and Spice Park, also in Homestead.