I believe the purple door has been replaced.
In version 0.99f, I went down a floating tile near the area the directions told me to go, and it was closer to the Onyx Flowers (Those flower-like objects you find scattered around the World.) then the other tiles. When I walked up to it and interacted with it, it took me to a field full of them, and there was a path that sectioned off into two different directions.
From there I took the left path(If you take it, you can't go back unless you revisit the area.), which brought me to another division, one path going up, the other going left. I went up, and it lead to the Flower World.
It let me return, so I took the left path, which brought me to the Blue Forest.
I haven't explored the right path yet, but I'll try to keep you updated.
((Sorry about the wall of text. ^_^')
Update: There is no right path. When you take the left path, it leads to the side on the right of the entrace anyway.