mmmm i have shot a series on the esplanade and i can offer you some pointers...firstly..i think you should spend your time more on trying to take away those ugly spots on the first photo rather than trying to get it all blue... and next thing is...having such a wonderful structure built..you shouldnt lose that focus on the subject...you lost some sharpness there...
for the second piece..i would try to shoot slightly underexpose for this shot to get the background really black..or do it so in photoshop...you get a stronger emphasis on the blue balls....