What is the participle adjective in the following sentence? : he was embarrassed by his picture on the front page.

The participial adjective in that sentence is embarrassed.  Participial adjectives perform the function of any other adjective, that is, they describe a noun. But they are often derived from verb forms, and so they may end in -ing or -ed.  

You can  chose any orange tee shirt to give to whomever you want.