Crochet help...

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Anyone have a link with really detailed, concise instructions for changing colour in crochet? I'm doing a piece that is all single crochet, but it changes colours from beige to midnight blue to black, and then reverses...all in the same row! So far, all the methods I've tried make the last (or first) stitch "bleed" into the new colour. This particular piece requires precise lines of colour. I need help. Fast. It's a birthday present for my landlady, and her birthday is the day after tomorrow!