I have been checking my wiring using a sperry instruments circuit analyzer before I sell my house and found a GFI outlet that shows the red on and both yellows. I took out the outlet and the hot an neutrals seem to be connected correctly as well as the ground. Any ideas? Take it apart and reconnect everything? I checkd all of the other outlets in the house and all test correctly.
Replace it. Electronics go bad
Hire a licensed electrician.
Hire a home inspector.
Is the home inspector going to make the corrections if needed? Most likely he will recommend having a licensed electrician make needed corrections. 
touch the wires with your tongue?
In most cases, when the three-light testers show all lights illuminated, the circuit is wired for 240V. Use a more reliable instrument and/or have it corrected by an electrician.