Legally, your employer is under no obligation to reimburse or comp Columbus day (or any holiday). It never hurts to ask, but most times they aren't going to do it. Since you're salaried, you're required to be paid for the whole week if work is performed. Whether they code it as 40 hours of regular, or 32 hours of regular and 8 hours of holiday pay, they're still following their legal obligation.

As far as Saturdays/Sundays, the big thing to keep in mind is that you are a salaried employee. That means you're paid for a week's worth of work. It isn't 40 hours, or Monday to Friday, it's just a week's labor. In addition, the Federal policy on travel pay for nonexempt doesn't require pay for travel on outside regular working time days. So a non-exempt employee would be in the same situation you are.

Aside from all of that though, it never hurts to ask if you have a good relationship with your leadership team and they feel like you're giving more than required. Many employers have more generous travel and holiday policies than the above.

At my current employer, if we require you to work on a holiday, we typically give you an alternative holiday in exchange. We also pay nonexempt employees for travel on the weekends (as required by law in California).