Can I change Bootstrap button color?

You need to override your css so you can change the background to black. A simple way to do this is to create a custom css class (you can either put this in a <style type="text/css"> tag in your HTML or put this in a separate CSS file)

.black-background {background-color:#000000;}
.white {color:#ffffff;}

Then, give your button these classes

<input type="submit" class="btn btn-primary black-background white" value="Text" />

This question has already been answered here: Styling twitter bootstrap buttons

I'd recommend following the advice above; common practice is to override the default/boostrap stylesheet with your own styles rather than edit default/bootstrap directly or adding new style classes. Foundation works the same way.