You can also use intarsia. For two color knitting with areas of color that span more than 5 stitches at a time, this is most often the method used. Be aware that with this method, wherever you have a new color section, you need a new strand of yarn. If you have a ton of hearts, it can get tricky just because the yarn strands love to all get tangled. Check out the video in the advanced techniques section.
Good luck on your project!
KnittingHelp Queen Bee
It is not because things are so difficult that we do not dare; it is because we do not dare that they are difficult.