How do you differentiate ejaculating and peeing in your bed when your sleeping?

Question

How do you really tell? Is there a color or something or an odor?

Answer 1

"YOU" don't. You're autonomic nervous system does it.
Read up on the autonomic nerous system on the internet if you do not know what it is to help you understand.
Should you be asking for the reason of wanting to know which may be happening with you and are embarrassed to ask those around you. Here's your answer... If you wet the bed, there will be a really big wet spot that will smell of urine if not dried by morning, if it is from ejaculation it should be a smaller spot/or spots - most of the time it will have dried somewhat and feels a little stiff.

Answer 2

Well you know what color pee is and more importantly what it smells like (Ewwww!). Semen is sort of thick milky white when you ejaculate, and then it thins out and becomes clearer. Unlike pee, it's sticky to the touch. It's got sort of a bleachy smell (like Clorox) to it.