Fall is in full swing here in northern Minnesota.  The colors have been beautiful.  I've seen more purple in the leaves this year and I was curious as to why so I looked it up online. This is what I found:

Anthocyanins

The reds and purples you see in the fall are caused by anthocyanins, which are what you get when sugars combine with compounds called anthocyanidins. Many things affect the exact color produced by anthocyanins, including the pH (acidity or alkalinity) of the cell sap in the leaves. With an acid pH, anthocyanins are often red; with a more alkaline pH they turn purple-to-blue. Because anthocyanins need sugar for their creation, weather that favors photosynthesis (sugar production) is essential. Bright, sunny fall days produce the best colors. Very little photosynthesis occurs on cloudy days, and rain can actually leach the anthocyanins and carotenoids out from the leaves. Different combinations of anthocyanins and carotenoids can result in there being yellow, orange and red leaves all on the same tree at the same time. The exact color a tree produces will vary from year to year. Some people believe they can force a more brilliant red color by adding acid-forming fertilizers to the tree, especially aluminum sulfate. This method may sound like it should work, but there is no scientific evidence to support it.

Click here to view the full article.  It is pretty interesting.  

Enjoy the rest of Oct.  The snow will be here soon.  Fall was about 2 weeks early this year they say.