color changing animation (new user)

i am making a animated cutout scene in time line can any one share video tutorial of this problem i am facing

i want to change the color of the capsule when it reach to cube and after few second capsule color will change by animation .. i made the animation the problem is capsule color start changing before it move to cube i adjust the key point timing then the animation time slow down please help me i am creating the capsule animation in same time line