Change Colors in JS(?) “Post Saved” Effect?

Hello- This may seem trivial but I’m stumped. When a post is published, there is a confirmation, (JavaScript?), effect above the window where posts are written. To confirm that a post has been published, the colors fade from yellow to the page background color. How can I change that yellow color? At first I thought it was a simple yellow graphic, but I could find no trace of this graphic. I’ve also looked through what I think are ALL the CSS files in WordPress but I can’t seem to find any reference to this effect I would like to change. Can anyone point me in the right direction? (using the latest version of WP)…
Thanks!!! DB~