User blog comment:AgentFlash/My Expectations For Sea Of Monsters/@comment-173.32.52.208-20120528132053

Based on this picture I think they did make Alexandra blonde...

http://www.percyjacksonmovies.com/wp-content/gallery/douglas-smithtyson/brandon-t-jackson-alexandra-daddario-douglas-smith-logan-lerman.jpg

And it gives you an idea of what Tyson will look like. Personally, I thought they just weren't going to include him, based on how faithful they are to the books :P