Hi John,
Semen can vary in color and consistency. Yellowish generally indicates it's "older" semen. That's part of why you have the wet dreams, to eliminate it.
It can be thin, it can be thick. It is almost never as thin as milk though.
You're NORMAL.
Nothing to worry about. Several things affect the consistency and color of semen, including your diet and the age of the semen. Unless the semen is noticeably pink or red, indicating the possible presence of blood, there's not much to worry about in the color of semen. Good for you for keeping track of these things and paying attention to your penis's health; go a step further and employ a top drawer penis health cream (health professionals recommend Man1 Man Oil) in order to maintain health at optimal levels. Choose a cream with alpha lipoic acid, which can help offset the harmful oxidative process that can occur in penile cells.