Thank you AndrsBrny for your explanation and clarification that 'piros fa' and 'redwood' are not considered equals. I've also gained a bonus with the knowledge that the mighty sequoias are known in Hungarian as 'mamutfenyő'. I'm enjoying the ride on this all encompassing Magyar learning curve! Duolingo deserves a 'thumbs up'.
My query about the 'redwood' seems to have provoked an exercise in semantics. This was not my intention, merely to ask if redwood is acceptable. Thanks to AndrsBrny and egyszervolt for taking up the challenge, but I suspect the discussion is off on a tangent. Here is a wikipedia link describing the entire species of tall redwoods (the sequoias) which grow in the west of North America and also China. They are massive trees yielding red timber - https://en.wikipedia.org/wiki/Sequoioideae - but like so many natural resources, are under threat. This is what I meant by 'redwood'.
Sorry for the tangent and for not replying to you directly. "piros fa" actually really just means "red tree", so you can't use "redwood" there. That species is called "mamutfenyő" which literally means "mammoth pine". I think we were just trying to get some colour terms and accusatives together.