Why did Belleek marks change from black to green?

Belleek explains that full production resumed in 1946 and the 4th mark introduced that year kept the prior design but changed colour to green. Testing suggested green showed less through the translucent body than black, making the stamp less visible when looking through the piece. That practical choice fits what collectors observe: Belleek’s thin parian can “ghost” a dark stamp from the inside under strong light. If you’re holding a piece with a green stamp that otherwise resembles the older black stamp design, that detail is part of why the mid-century change happened.