Much of our board is orange against gray..Is there a way to replace the orange with another color ?
You should try looking around your index.css file for that theme and changing the relevant colors (which will probably be mostly in hex format, like #0334ff and etc). Inspect tool from browsers should be useful to find the relevant parts, some let you pick the colors from there too, like FF.
If the theme uses images you'll have to find and edit those, too.
Thanks, FortyTwo... :)