Texture appears pink in Blender Render The tree on the left is always purple, whenever I try anything, like changing the material, texture etc. it always turns out purple.



It's fine in cycles:



I've been following a tutorial by CG Geek on youtube and have had no problems up to about 1:01:39. But now when I try to follow along my left tree always appears purple as shown in the picture. The tutorial is here.
You're trying to use a cycles material with blender internal. This probably happened because you created your material with cycles selected and changed to blender internal. Materials are specific and can't be used with both renderers.

You can choose to change the renderer to cycles (1)
You can unassign your material and create a new one (2)
You can remove nodes from your material and modify it to be blender internal (3)