It's lovely with just the colors you have in it - do we hear an echo in here?
In the close-up panel - the "bright" color looks like tangerine (orangy red) to me instead of fuschia - which to me is red with a hint of blue in it.
How about making a small pillow with the accent color(s) you are thinking about using and go from there?
As long as you are using the "window" theme, I think I would like to see "plain" borders that resemble window frames and sills.