Black Bordering in OpenGL

I am working on an application where graphics symbols like circles and rectangles have to be overlayed over a texture. Sometimes depending on the color of the texture, these graphic symbols are not clearly visible.

We have come up with a scheme to draw black border of 1 pixel width around these symbols(inside and outside of rectangle) to make it stand out, depending on the texture background. How would this black bordering be implemented in OpenGL?

R Gopal