Okay just got caught up. I have been so busy. Forgive me. Vicki's so helpful in reminding me to get over here. (I'm taking my Masters classes).
Sooooooo, I would buy KRYLON paint for the base. I painted these chairs 8 years ago and while they are very slightly faded, it's not much at all.
I used Krylon for plastic but also sprayed it on a metal table and it's still perfect. I believe the can says it's good for everything.
Then you can use an exterior paint for houses for your design work. Example: Lowes sells small 2 ounce cans (or something like that). If you were doing a giant flower on each one all you need is green and the flower color.
All paints do fade over time but since I imagine these culprits would ruin the cans, I wouldn't worry about time.
Can you just order a giant bolder to be placed in front of the fence?
I hope this helps.