First of all ... what an interesting pattern, done with the triangles! I like it!
It's hard to tell as the pics show different colours. In the first pic, the green looks very dark and the last, it appears brighter. I'm thinking the last is closer to true? Further, the sunflower in the last appears to have two different yellows, which I doubt is correct.
Also, without knowing where the pattern is going after you get this first block figured out, it's really hard to know what might be best overall.
From what I can see (and guess), I think the green works well. I think I'd be more apt to change the yellow into something more vivid (same strength of colour as the others you are using) ..... and again, maybe it is, and it's just the way it's showing on my monitor!
I like this pattern .... and look forward to seeing what it turns into!