blue bits of paper
blue stickers
blue tape
blue streamers to tear
blue lids
blue beads
blue poms poms
blue feathers
bottles of glue (hmmmm….that rhymes with blue!)
since the favored technique was putting the glue on TOP of the collage items, i’m glad it dries clear.
newcreationpreschool.com 
You could also change the color of the glue with water color, paint, or food coloring.
I love this idea! Looks so fun, and collaborating is a great skill, too! Fits in well with my focus on reusing/recycling materials – we might have to try this in my classroom!