What sea doesn't exist- black yellow blue or red?

The Yellow Sea is the sea that does not exist in terms of traditional naming conventions, as it is not recognized as a distinct body of water like the Black Sea, Red Sea, or the various blue seas. The Yellow Sea is actually a marginal sea located between China and Korea, but it is often simply referred to by its geographical name rather than by the color it represents. Thus, in this context, it could be seen as the "sea that doesn't exist" among the color-based options provided.