I noticed that sometimes some stitches didn't seem to show up that well. They were kind of "hidden". I wondered why? Then I got the wonderful book "The Essential Guide to Color Knitting Techiniques" by Margaret Radcliffe and found out WHY and what I was doing wrong!!
I knit Continental style and hold the two colors in one hand. I didn't know that it made a difference in what position the yarns were on my finger as I knit. In other words some times the pink yarn would be on the top and the black yarn on the bottom across my finger and visa versa. In her book she says that "It's important to be conistent in how you position the yarns because this affects the size of the stitches in each color!!