The standard solution is to have the foreign text on a float which covers a small part of the viewport, e.g. white text on a black rectangle.
You can make it look better if you choose a text color which is by itself likely to have high contrast from most other colors (your current white is great here) and give it a very fine border from a color which will have high contrast from the colors the main text disappears within.
You can also programatically change the color each pixel of the text depending on the background.
You will never achieve a subtle, beautiful effect - these are impossible under the circumstances. The design look and feel will change a lot. This is a necessary price for readability in this case.