It is possible to have all blue (/green). Even after adding new JDKs and Central switching to https I've been able to get all masters back to stable.
As you might see right now a couple are failing. It might be an infra issue (broken Jenkins node) in which case you can exclude that node .
For the same reason, start with a branch before pushing to master. Once you've seen all blue on the branch, you should merge back to master.
If tests are broken, I will ask the committer to fix his commit. If that requires some assistance, I can help.