"A purple flower."
Piws is used in North Wales as a translation of purple, although it's standard meaning is 'puce'. Porffor is the standard translation of purple.
Thank you for helping again, rmcode! It would be nice if Duolingo presented some of these extra words before marking us wrong for not getting them right at first sight. Still, I know that the Welsh-language section is still in Beta!
Yes, it is very frustrating for us not being able to present new words and the simplest sentences before more complicated ones. Once we've finished correcting the course, one of our priorities to investigate why the Duolingo alogorithm is producing sentences in such an illogical way.