Take a look at Colour Me Beautiful by Carole Jackson. It's a clever system that really works. The basic theory is that you will look best in colours which harmonise with your natural colouring - hair, eye and skin colour.
Shopping is simpler. I know which colours to hone in on and just ignore the rest - a real time saver. If I stick to 'my' colours I know that any new item I buy will harmonise with everything else I've got. It saves me time and it saves me money. Simple!
(The original version is available for 1p on Amazon - used, like new - I don't know what the later versions of the book are like, but the principles remain the same I'm sure, though of course the illustrations are dated - and the title always was a bit naff! But it's really worth having........)
next - what is style anyway, and why would I want to look stylish?