I am creating assets in blockbench and exporting the assets as obj directly into the custom collection I have. When I open it in AssetForge and I go to my custom collection I see the model but there is no color. 

In the folder I have 

test_block.obj

test_block.mtl

texture (which is supposed to contain the textures for the obj)

Textures aren't supported for custom blocks, they have to use materials with colors however not textures as UV maps are overwritten by Asset Forge