Before Rebase flowchart

The flowchart above represents a normal git workflow. In the middle with the blue color you can see the  master branch that has already 4 commits to its history at the beginning. Then 2 colleagues decide to split up and take over one part of a new feature each. Thus we can see that 2 branches were created. At some point the green branch has finished first on it's local computer, merged to local master and pushed by updating the remote master.

Question:  Now that green branch has fulfilled it's purpose, and the red branch is still in use, how can the man who works on the red branch and has already made 4 local commits, fetch the new changes from the remote master and merge them to it's own branch, but by keeping his own commits also on top?