I have seen many occurrences of this phenomenon while dealing with Woody Weeds on the Mt Painter Nature Reserve. What seemed to be a single plant with red and green branches. I dug an example up and found that they are two separate plants. The third photo is another example of this. I suspect that happens when a bird dropping with more than one seed germinate. I have seen other examples where two different plant/weed species are growing within a cm of each other. Further speculating, I think the parent plant must be a hybrid or heterozygote segregating and the two different coloured seedlings reflect segregation for red and green phenotypes