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
"There is a vitality, a life force, an energy, a quickening that is translated through you into action, and because there is only one of you in all of time, this expression is unique. And if you block it, it will never exist through any other medium and it will be lost. The world will not have it. It is not your business to determine how good it is nor how valuable nor how it compares with other expressions. It is your business to keep it yours clearly and directly, to keep the channel open. You do not even have to believe in yourself or your work. You have to keep yourself open and aware to the urges that motivate you. Keep the channel open."
— Martha Graham