I've been using f.lux on my computers for years. Now I've come up with a way to make my iPhone and Kindle have orange displays, too.
Looking at blue light after dark affects sleep. f.lux is a free app that removes blue colors from your computer's display when the sun goes down. My wife and I use f.lux on our laptops and desktop machines. I had f.lux installed on my iPhone when it was jailbroken, and it was great for bedtime use.
I haven't gotten around to jailbreaking my iPhone 6 Plus, but for now I'm happy using tinted orange film as a blue light filter. Amazon sells a 12-pack of 8.5 x 11 orange plastic sheets (enough for dozens of devices) for $(removed)
Here's my go-to kit for cutting flat material: metal rule, snap-blade knife, and cutting mat. I've had this same self-healing cutting mat for 30 years and it is still going strong! I expect I'll have it for the rest of my life. If you don't have one, get one. You won't be sorry.
After trimming the film to size, you can just lay it on a Kindle display. Static electricity with usually keep it in place. If not, rub the film with a cloth to build up a charge.
For an iPhone, I used bits of tape to keep it from sliding off the screen.
Little pieces of paper at the ends if the tape make it easy to peel off on the morning. Eventually, the tape will lose its stickum and you'll need to replace it. I'd love to hear suggestions for making it easier to attach/remove the sheet from an iPhone.
If you think that blue light's effect on sleep is hokum, or that this orange film will not help anyone sleep better, please use the comments as your personal anti-woo crusader soapbox!