Some have the opinion that cold noodles can be taken more deliciously when accompanied by mustard and vinegar, but others maintain that cold noodles can be best appreciated by taking noodles and soup only and without condiments.  Of the two different opinions, it is generally accepted that eating cold noodles along with mustard and vinegar are better, since the condiments not only give sweet and sour taste but also gives other benefits to human body.
Being a kind of warm food, mustard helps protect the warmth of body when put into cold noodles.
Vinegar has the function of dissolving lactic acid, and therefore, it is helpful for fast recovery from fatigue.  In addition, vinegar can suppress propagation of colon bacilli in summer season when cold noodles consumption is at its peak.  The colon bacilli are most active in the neutral state, but vinegar makes noodles become acid, thereby exterminating the bacilli.

To appreciate the deep taste of cold noodles, it is desirable to take noodles like coils without cutting them with scissors. 
Hamheung noodles, for example, are made with starch of potato or sweet potato, so the noodles are thin and rigid, and their unique flavor can be fully appreciated when taken without cutting, like spaghetti.
Pyeongyang noodles are mostly made of buckwheat, which are thicker and more easily cut, but the aroma of buckwheat can be smoothly enjoyed when taken not as pieces but as coils.

If we eat egg yolks beforehand, it will eradicate the vestige of other foods remained inside mouth, thereby enabling us to taste cold noodles fully. 
As noodles are made of buckwheat or potato, they can give trouble to stomach wall if taken when stomach is empty.  Taking egg yolks first will alleviate such burden to the stomach and thus facilitate digestion of cold noodles.