The Redmine developers turned off Textile inline styles because of a security risk with XSS attacks. I explain below how to turn the inline styles back on if your Redmine server is protected from unauthorized access. I would suggest keeping textile styles off if your Redmine server has public access. The main point of this article is to point out that the styling such as background colors, css, table borders, cell borders, etc. is turned off by default.
If you do decide to turn inline styles back on using the information below then here is a note from the Textile Reference Manual (link):background, border, formatter.rb, inline style, redmine, self.filter, textile, textile format, XSS, XSS attack