There is an advantage to using modern mass produced yarns. This afghan (a modification of Nicky Epstein's Tree of Life) was knit with Vanna's Choice. It wasn't my choice. I wanted green and washable. My pocketbook dictated the rest.
The advantage? ~ I bought the yarn before settling on my pattern, which called for 10 balls of yarn. I only had 8, so I made the afghan a little smaller ~ but I still ran out of yarn. When I went in for more, I wasn't able to get the same dye lot ~ but the color is so close that I can't tell the difference.
My mom taught me a trick for mixing dye lots, when you have to. You alternate for a few inches, knitting two rows of one dye lot and then two rows of the other, thus avoiding a sharp line where the color changes. I didn't bother to do that. I actually ended up with yarn from three different dye lots, but they are impossible to distinguish.