How do I get rid of the yellowed "faux water" in a vase with faux tulips?
According to this article, https://www.hunker.com/13419686/how-to-remove-acrylic-water-from-a-vase
you can use acetone
Soak with vinegar
better to not use faux flowers.
You. May find it may not be worth the trouble. Not always so easy to do. I just donated mine to Goodwill.
It is made so it cannot be removed. Ditch it and get a new vase at goodwill for one or 2 dollars.
Sadly there's not much that can be done to change the color. What you can do, if you still love the flowers, is give them a good cleaning and then wrap the bottom half of the vase in manila rope to give it a whole new look. I used manila rope on this project and it's thin enough that I think it will look great on your vase - https://www.girljustdiy.com/rope-planter-basket/