Sewing sharp corners or curves can be difficult, especially for the beginner.  When it comes to color blocking, I think there is even more pressure, because the end results are more obvious, especially if there is a mistake.  While sewing well does take some practice, we go over how to tackle those corners and curved seams.  The most important step is to take your time and practicing with scraps.  We go over two color blocking examples in this tutorial.  First we tackle sharp corners with McCall's 6792, which inserts a rectangular shape into the front of the garment.  I demonstrate two techniques you can use to guarantee a perfect corner.  Next, I show you how to work with curves in Vogue 8923, which is a dress with beautiful color blocking possibilities.  If you find doing curvey seams are difficult, then draw a circle on printer paper and just practice trying to sew your lines.  (Be sure to use an old needle and you don't need thread for this exercise.)   While these skills seem fairly easy and straightforward, they definitely are harder than they look, especially if you want them perfect.