I am knitting a sweater and one half s one color and in the middle of the back on the same row you change colors of yarn... How do you change colors .... When I changed colors it left a hole....
When you join the new color, bring it underneath the old color when wrapping your needle. This catches the old color and will float it along. Think of it as twisting or twining them together. You could also knit that first stitch with the 2 yarns held together. Since the new color is the now dominant, the old color will fall to the back and won't be visible. Also, leave a long tail so if you still get a loose join, you can just fix it when weaving in your ends.
Hope I helped!