Wiring Help Lutron Diva Dimmer and Claro 3-Way with Claro First in Line
In many 3-way diagrams you will have the feed come in to one switch, and the outgoing wire to the light at the other switch.  You have the feed and the output in one box, so you need an extra hot wire to go between the two boxes.  Because you have a green wire, I think you might have conduit.  If that is the case, the best option is to run another colored wire between the two switches to act as the common wire to the Diva.

If you cannot run an extra wire, you can use the white wire as the common return, and you note that by marking the white wire with black tape (because it will be a hot wire in this scenario).

In either case, the wire connections should be as follows.  On the Claro, connect the black wire that is the power into the box to the different-colored screw on the outlet.  The red and black "travelers" that go from box to box will connect to the other two screws.  The whites from the feed and the output to the light should be connected together.  The common return (new wire or black taped white wire) will get connected to the black wire that goes to the light.

In the Diva box, the taped white wire will go to the different-colored screw, and the red and black get connected to the other two screws.  And of course, all grounds get tied together and attached to the two switches.