What grains are used for making LME/DME ?

I tried searching the forums, but that didn't yield much.

I was just wondering which specific grains are used for making DME/LME? I am trying to narrow down flavors in my beer and for the recipes I am working on...

Is there possibly a website or listing that could explain for the various types? Are they a mix of grains? I could guess that different companies use different types and mixtures.

It depends. Each manufacturer makes their own. Generally, the "light" extracts are just two-row or pilsen malt. But the darker ones might have crystal added. I'd check the manufacturer's website if you really needed to know.

I would probably just always buy the lightest extract, and use steeping grains to get the correct color and flavor, that way you know for sure what the ingredients are.

Some manufacturers tell you, some don't. Briess lists the ingredients on their extracts, but not the percentages. Munton's IIRC does not list it at all. You have to check their websites. You hear/read unverifiable rumors from questionable sources from time to time, the bottom line is don't assume any specific makeup unless you get it from the manufacturer.