Discoloration can point to contaminates in the sample, such as blood or urine. Take the semen sample and record the gel-fee volume of semen, amount of gel collected, and total volume of the ejaculate. Record these numbers for your records. Also note the time since the stallion's last collection or mating. Phase contrast microscopes are by far the most superior microscope for this process but are not required.
Many people use inexpensive hobby microscopes for farm or personal evaluations.
The goal is to make sure sperm cells are present in the sample and moving. All moving cells are considered motile and this movement is referred to as Motility. Then, look for sperm cells that are going in a fairly straight line and have forward motion. This sperm movement is termed progressive motility. Non-moving or circular sperm will not usually cause a pregnancy, therefore are not counted toward progressive motility.