a cheap and effective palette which cleans easily
Buy one of those enammelled plates from your ironmongers or better still, try to get an old enamelled butcher's tray from a junk shop.
When you have finished painting, scoop off any unused paint you want to keep and dunk the tray in hot water. Even old dried paint will come off after a little scrubbing with a stiff brush. The paint will peel away easily.
Make sure you don't block the sink!