How did you make this? The cast shadows are at different lengths so it wasn't using the same method I used. Plus you have multi-stud bricks! But I think adding a highlight after colorizing would help the whole image. It looks like the yellow ones in the lower right side are highlighted.
I used a program called Bicksaic to create it. I'm running a new computer so I haven't reinstalled all my stuff yet to be able to tell you where to go it. But it creates files in LDRAW format. Then I used a program to convert the LDRAW file to a POV-Ray file, and I rendered it. The highlights are because there are 3 lightsources, and one ended up near that corner.