How can I change the outline color around discussion comments?

Many of my students are older, and the current outline and color around the comment entry box is so light as to be nearly transparent. I would like to darken and thicken the pixel size of the outline for the comment entry box. I would also like to change the button from "Answer the Question" to something else, such as "Submit Your Reply."

Also -- and I've been asking for this for ages -- I would like to allow students to format their replies within a discussion. Right now, the text all flows together without paragraph breaks. I know there's a WYSIWYG editor associated with those comment posts -- so how do I let the students use that editor?