I used to live with a Korean roommate. He cooked for me the cool noodles 3 times.
It tastes exactly like the one in restaurents
I think I could remember 80% of the stuff he put in for the red source.
The thin noodles are brown color which you can get it from most of Korean stores.
1. red hot korean paste + Korean red hot powerder(optional)
2. some sugar + some salt
3. some sesame + some sesame oil
4. garlic powder
5. grind cucumber
Grind all the ingredients and you get urself some tasty source. Btw, he always puts a couple of boiled eggs before serve.