I'm a big fan of the Levi's 512 bootcut jeans, but have discovered in the stores that if you switch colors you may also be switching sizing and fabric.  The jeans are apparently manufactured in different countries with each their own interpretation of size and acceptable fabric content.  A dark wash may be a perfect fit, but if I try, for example, a black 512, the sizing is completely different: big/small/long/short/or unusual waist sizing.  I took a chance on ordering the Midnight Star color thinking that it was what I knew from in-person shopping.  I ordered my usual size and they were at least two sizes too small.  Additionally, the fabric content was 24% polyester (!) whereas it was listed as 14% polyester in the description.

Note: I actually like the 14% poly/lycra content that I have purchased in-person:  it makes for a nice smooth jean fabric that looks a lot more polished than those with more cotton.  But when it becomes 24%, the fabric starts to look like an inexpensive knock-off of denim.

I strongly suggest that the Levi's company get their sizing and fabrics standardized.