This article is a miscellany of the odds and ends of other trees I have encountered while looking for those main four groups. Some are called dragon's blood in their areas and some are just bloodwoods. These articles are going to be lists of the various plants with a few details on each, not exhaustive monographs on each plant. The article on Dracaena will be more in-depth, as there is a lot of information on those trees.
A surprising number of these trees grow in swampy or frequently-flooded areas. The pigments may have an antibacterial and antifungal effect, helping to preserve the wood from rotting in the damp conditions. There are, of course, many, many other trees with red wood but I have tried to restrict this to those that have been compared to blood.
The mineral pigment red ochre or ruddle has been used by humans for a very long time. The earliest reliably-dated finds in human sites are from about 200,000 years ago in both Africa and Europe. Red ochre seems to have been used for a wide variety of purposes from rock paintings to decorating skeletons. Scholars often resort to the "it was religious" argument when they have no evidence for context or other theories for a practice by ancient humans. Some of that use of red ochre may have been religious but it should be noted that modern hunter-gatherers use red ochre for decoration, tanning animal hides and as an insect-repellent. Australians were using red ochre at least 40,000 to 60,000 years ago. There were underground red ochre mines in Australia at least 32,000 years ago. Red ochre continued to be mined from several locations and was traded throughout the history of Australia.
Red ochre is a relatively dull pigment compared to the bright and deep reds seen in many plant dyes. We cannot be sure how long these plant pigments have been used by humans as even the most stable of them tend to break down over thousands of years. We can be sure that these plants caught the eye of ancient humans just as they were used all over the world in large quantities throughout recorded history. The many plants that bleed red blood like a human would have been especially fascinating.