Chrome removed it 4 years ago: https://chromestatus.com/feature/6607299456008192 Alternative is background-blend-mode
Created attachment 447946 [details] [fast-cq] Patch
Committed r287433 (245568@main): <https://commits.webkit.org/245568@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 447946 [details].
<rdar://problem/86897148>