Here are the magic words that let you search for all bright blue galaxies:
select p.objid, p.ra, p.dec, p.g, p.r
from photoObj p, specObj s
where p.specobjid = s.specobjid
and p.g-p.r < 0
and p.g < 15
and p.r < 15
and s.specClass = 2
Don't worry, you'll learn what each of these terms means later in the tutorial.
If you enter these words in the SQL search tool, the tool will return eight galaxies, with object IDs below. Click on the links to see the galaxies in the Object Explorer. Which ones really are bright blue galaxies? What are the other objects, and why did your search return them?