Question
I have always had a very nice looking yard.  The yard has a nice normal green color to it until I mow.  Once I mow the yard has a very yellow hue to it.  I have sharpened the mower blade, as well as, put a new blade on the mower.  Nothing helps.  I am in Colorado and have Kentuck blue grass.  I use Scott's turfbuilder II every 6 weeks or so.  Why is my grass looking yellow once it it mowed?

Answer
That's pretty simple actually. The only parts of the grass that turn green are the parts that are exposed to sunlight. The lower parts of the blades are typically brown/yellow. When you mow, you cut off the green and reveal the yellow.

Try mowing more often. When the lawn is allowed to grow longer, more of the lower parts of the blades are hidden from the sunlight, and therefore turn brown. When you mow more often, the lower parts are more exposed to the sunlight and stay greener.

Good luck!

-C.J. Brown