There are plenty of glass block designs and colors in the market. We chose the "Diamond" design with no color (clear). This design seemed to shimmer in direct light. Other glass block suppliers call this design "Regent", "Checkers" and "Jewel".
After the house construction, I wrote how the glass blocks provided natural light to our living room especially near the stairs.
And the natural light was quite effective. The dark varnished steps of the stairs are brightly illuminated anytime of the day.
Shown below is a photo of the stairs, looking down, as taken from the stair landing. You'll notice how brightly the glass blocks (on the left) are from the sunlight.