1. I always mix nail polishes, as lets be honest, I am not about to go out and buy an new colour every time I need something really random, such as a certain shade of yellow or something that I would never use again. so I mix my colours from my existing polishes which is perfectly fine. 
So these are some of the things I use as a kind of pallet to mix the shades that I need. I am not very fussy, here I have used a block of post its, and the lid of a box that I keep some of my polishes in, but in the past I have used anything non porus that I have to hand. Just add a small blob of the colour that you want to mix to create your shade and then mix them up in small quantities as you go as they will dry when they are outside of the bottle and you you want to avoid wastage and you will need a nail brush as if you use the brush with the polish, the whole polish will be tainted.
Anooother really useful tip is that when you dislike the colour of the whole bottle, maybe it looked different in the shop, or some of them change in exposure to light etc, you can mix the colour all in the bottle, by pouring in white polish, you can lighten a shade, or darken by adding a few drops of a darker shade of the same colour. Just shake well and you are done!
Anooother really useful tip is that when you dislike the colour of the whole bottle, maybe it looked different in the shop, or some of them change in exposure to light etc, you can mix the colour all in the bottle, by pouring in white polish, you can lighten a shade, or darken by adding a few drops of a darker shade of the same colour. Just shake well and you are done!
