rendering tesselated of non convex polygons

Hi, I have implemented my own tesselation algorithm for non convex polygons but I am having some difficulty rendering the result nicely. It is based on the code project article

It works very nicely, however, my problem is that I want to see a solid colour, but the edges of the polygons appear to blend, so the result is that I see the boundary of each triangle.

Can anyone tell me what mistake I may have made in the GL state for this to happen and what can I do to correct it?