Looking for a way to put led brake light strips 2 side by side on both bed side ends,

[Sickboys]

which custom car tv show did a custom truck with hiddeen led brake lights coverd with paint so they were only seen when the brakes were applied .. I have a 64 c10 swb bw and I put caddy taillights in the back, I'm still in the fab stage So changing them is not a problem. What I would really like is 2' long side-by-side LED strips on each side. There was ATV show I believe it's on velocity or discovery that they did this and I believe it was a 3 stage candy color and they sprayed the candy color over the Strips and you couldn't see them until the brakes were depressed. Anybody have any idea on what they used and how to do it. Thank you in advance for your time.