Pour it in a swish around. Just for looks,right?
Here's how we tinted a bottle
If you want it opaque, just put your latex or acrylic colored paint inside the bottle, turn it on it's side and gently roll the bottle around to distribute the paint. Then turn it upside down so that it comes into the neck of the bottle so that you can cover that part too. You can use more than one color if you like. Just roll the colors around gently until you achieve the look you like. Let it dry and you're done. Wishing you the best.
Pour some paint in, cover the top, and give it a shake.