Paint Details - Add Detail Mesh - 50% of the meshes Unity paints turn red.

Ashervisalis

For some reason half my grass is red. I've messed around with the healthy & dry colour to no avail. The texture is completely green, and so is the material ball. The model also looks green in the viewer (in the bottom right of the screen) when selected, it only starts turning red when painted. It does this when I try painting any Detailed Mesh. These meshes were from Unity's 3D Game Kit - Environment Pack.

Thanks in advance for any help