I noticed a recent kbase stating that it was not possible to alter the font, size etc. of a message box. This is not strictly true. There's a .net dll available at http://www.news2news.com/vfp/?solution=5 that works in Progress. You just need to run some progress code that loads and configures it and all subsequent message boxes throughout the Progress session will have the new styling.
This in not a free tool. It looks like they're charging $50 for it now. I have no connections with the developer, I'm just a user.
Here's some sample code I use for presentations.
DlgMgr:AssignMessageFont("Arial", 16, 0, 0, 0, 0, 0).
DlgMgr:UdfBackcolorsEnabled = TRUE.
DlgMgr:DlgMonitorEnabled = TRUE.