This comes up a lot on here, K. Several ways of doing it............
Take the doors to a car sprayshop. They'll hang them up and spray the lot in any of the hundreds of auto colours available.
Buy primer and colour from Halford's, in aerosol form, and do your own.
Lightly rub down and de-grease; then, preferably use a primer for plastics and non-ferrous metals such as "Zinsser". Then brush or roll with anything you like.
The key thing in a kitchen is to use a degreaser because no matter how clean your doors look to the naked eye, invisible grease will have become ingrained over the years. I used a product called Krud Kutter (mfd. in the US). Do not short-cut that preparation, or your paint will be peeling off very soon. Then an undercoat especially if you are changing the colour, and a final 2 (at least) coats of paint.