What's normal? - a concerned mom's question

I have a son who is a teenager, and is also a quadriplegic and in a wheelchair.  I am the sole caregiver for him.  We have, you can imagine, a very open relationship about the changes in his body.  There are (unfortunately - sometimes) no secrets.

As I'm not a male, I've no idea what's normal as far as the developing male body's semen.  We've noticed in the last few days that he has wet spots in his underwear and there is a stronger smell.  I believe (the shorts are gray) that there is some color to the spot, too... possibly a lighter yellow/orange.

I've searched the web and have seen there could be color or odor due to his straining/constipation and blood being in his ejaculate.  Is that true?  Or is this a normal part of him growing up?  The smell bothers him -almost- as much as myself.

Thank you for any help you can give us.