Hello. Recently I was testing all these extractors so I wanted to craft, among others, iron and cobblestone ones. I looked into JEI and I was surprised when I noticed that the darker one is crafted from iron and the lighter from cobblestone. This looks inconsistent, because cobblestone pipe is darker than the iron one. I think that the iron extractor texture should be replaced with the cobblestone extractor texture and the cobblestone extractor with the iron extractor texture.

Now it looks like this...

...but I think it should looks like this.

The iron extractor texture is based on vanilla hopper. I think I do not have to change.

Oh, I didn't think that the icon is based on Minecraft's hopper. My first thought was associated with items colors, from which these extractors are made. I don't know if I'm the only one who had these associations. If not, you should consider texture changes to be more consistent with items colors. It's your mod, so you can do what you want :)

Color-based extractor textures