Did dinosaurs have red or white meat? Typically, we think of white meat as coming from poultry, such as chicken, duck, turkey, while red meat come from large mammals such as cows, pigs and deer. So if you were to hunt down a stegosaurus or a triceratops and cooked it over a barbeque, what colour would their meat be?
The redness of meat comes from a protein called myoglobin, which carries oxygen from the blood to the muscle cells. It is similar to haemoglobin, which gives blood the characteristic red colour. An important note is that when you see reddish water drip from meat from the butchers, you are seeing myoglobin, not blood (the blood is drained when the meat is prepared).
The difference in colour between red and white meat come from the type of muscle fibres and their myoglobin content.
Red meat is made from slow-twitch fibres, which are useful for sustained activities such as walking or to keep standing. They exert a smaller force over a longer period of time, meaning they require more oxygen for aerobic respiration (a more efficient way of burning fuel using oxygen). Ergo, red meat is full of myoglobin, hence its deep rich red colour.
On the other hand, white meat is made of fast-twitch fibres. These fibres are better suited for quick bursts of energy, such as flying or quickly responding to a threat. These fibres use anaerobic respiration (no oxygen), which allow for a quicker, faster burn of energy, but only for a short time. In birds, the breast muscles are typically very white, but they do have some slow-twitch fibres in other muscle groups such as their wings and legs, which is why there is a distinction between light and dark meat.
So how about dinosaurs? Dinosaurs are the ancestors of birds and reptiles, so it would make sense for them to have had white meat. However, the majority of dinosaurs, especially large ones such as sauropods, would have had very powerful muscles with slow-twitch fibres, making their meat quite red. A good example are ostriches. Even though they are birds, their meat is as red as beef because they have powerful leg muscles for running.
Smaller animals such as raptors probably had more white meat akin to modern poultry, as they would require sudden bursts of energy for ambushes.
As for how they would taste, that is something we could not answer until Jurassic Park becomes a reality.