What pattern do you use to crochet colourful headbands and beanie hats?

I need to know what pattern you use to crochet a headband or a beanie. For a headband, is it possible to join TWO DIFFERENT COLOURS of yarn and more to make stripes or weird patterns or do you have to buy ONE ROLL OF YARN THAT IS MULTICOLORED? I have a headband that is striped colours and it looks like it was made with separate rolls of string joined together somehow. PLEASE HELP! I REALLY need some help on how to joins separate yarns and make colourful odd patterned headbands mainly. Anybody who really helps me will get best answer!