Mulberries, despite appearances, are not related to blackberries and raspberries and grow on trees rather than canes. It's been so long since I've had a red, or American, mulberry that I don't remember what they taste like, and I've never seen or tasted either a white or black mulberry. Blackberries and raspberries are both members of the genus Rubus (as are dewberries, cloudberries, thimbleberries, and salmonberries, none of which, as far as I know, are cultivated commercially). Dewberries are similar to blackberries while thimbleberries, which look like a strangely formed raspberry, don't have much flavor at all. I've not had an opportunity to try either cloudberries or salmonberries. Crosses between blackberries and raspberries include loganberries, tayberries, and boysenberries. Loganberries are more tart, and tayberries less tart, than blackberries. Both have a distinctly different flavor than blackberries. Boysenberries are slightly less tart than many blackberry varieties and tend to be larger, but I don't find their flavor difference to be much different from blackberries -- more like the difference between different varieties of blackberries (e.g., Marion, Chester, Brazos) -- compared to the difference between blackberries and tayberies or, especially, loganberries. The red raspberry is probably the most common raspberry type but there are also yellow varieties that are very similar in flavor. The yellow raspberries I have access to tend to be even more fragile than any of the available red raspberry varieties. Black raspberries are smaller, have a higher proportion of seeds, and are less productive than red raspberries, but they have a distinctively different flavor that makes them worth searching out. Red raspberries seem to me to have a brighter, sweeter flavor than black raspberries. There's also a purple raspberry that's a cross between a red and a black raspberry, but I've never tasted one.