How to restore the color in my vinyl shutters, they are frayed?

Remove them, clean them with a garden hose - soapy water, and spray paint them.

Clean, prime with primer for hard to paint surfaces, paint.

take the shutters off, clean,spray paint with rustoleum 2X for plastic applying two light coats allowing to dry inbetween,seal with a UV clear spray

Clean and paint with a paint made especially for plastic..

I recommend Rust-Oleum's Painter's Touch spray paint. Use it on my plastic lawn chairs. Could not ask for anything better.

This product has good reviews please check out the Q&A and reviews to see if might meet you needs. I have outstanding sucess with Rustoleum products, but have not tried this one. You might call their 1-800 too.

https://www.amazon.com/Wipe-New-Rust-oleum-R6PCRTLKIT-Applicator/dp/B01D1XIRDY/ref=pd_lpo_vtph_60_tr_t_2?_encoding=UTF8&psc=1&refRID=EA9FQTEK4JT9ZPS26E1A

You can paint them. Take one to the paint department of the home improvement store and ask them to select the correct paint for this project.

There is paint used for vinyl just like this: https://smile.amazon.com/Rust-Oleum-1909830-Vinyl-Spray-11-Ounce/dp/B000KKMVMK/ref=sr_1_8?ie=UTF8&qid=1523321998&sr=8-8&keywords=vinyl+paint