Hi sirofsirs, aka Matt, welcome to the board!
You can change the color (format) of a cell with Conditional Formatting, found in the Format menu. The Help files should be sufficient on this, but if not do a board seach for it and you will have more than enough info to get the job done.
As far as sending out an email, that is asking quite a bit more and you'll need VBA for that. It is a very large jump from coloring a cell to sending out an email. Could perhaps something else trigger the event to send out an email? Perhaps a user's keystroke or clicking of a button perhaps? This is generally a *safer* way to go. Of course, anything can be done. If this is what you would like to pursue, please provide all details necessary, such as email client, to, cc, bcc, subject, body, etc.