Dependancies between projects based on milestones

Hello everybody,

I want to manage dependancies between 2 projects led by 2 differents teams.

If I link a task on the first projet (supplier) to a fixed milestone on the second project (customer), it works well, as I expect it to do. The milestone is displayed in green or red as the constraint on the fixed date is respected or not.

My question is how to do this between 2 milestones?
I'm aiming to do so:

Project 1 (supplier)
Milestone A (floating milestone) : delivery of XXX
Project 2 (customer)
Milestone B (fixed milestone) : supplying of XXX by project 1, Milestone B is linked to Milestone A

Unfortunately, it seems not working, milestone B is always green.

Thanks for your help,
Stephane