Paint Swirled Ornament: Question

How many bottles of paint do you think I need for 100 glass ornaments? We are doing this for our 5th grade Winter party craft.

Response from Crafts For All Seasons:

How fun! I think this craft would be great for fifth graders. If you use two colors per glass ball, I would estimate that two 2 oz bottles of acrylic paint (one of each color) could make at least 12 ornaments. So for 100 ornaments, I would buy eighteen 2 oz. bottles total (9 of red and 9 of green). I don't have experience making these in quantities, so I'm taking a guess here, but that is my best estimate. If someone else with experience would like to comment, please do so. After you complete the project I welcome you to come back and comment on this post and let us know if you had enough paint. Good luck with the project!