I am having this same problem.
I just learned to knit using YouTube. I have to agree that Knit and Purl look exactly the same! My goal was to do one ball of yarn in Knit stitch and one ball of yarn in Purl. My confusion is that they do look the same. I don't see any difference in the stitches. Does the difference only display when you Stockinette or Ribbing?
Also, I am having problems getting the correction tension now that I am purling. I moved up to continental method for the knit stitch, and since I am just starting to practice purl, I am throwing the stitches. My tension is just lacking and I don't know how to fix that.
Any suggestions would be helpful.