Sometimes these marking can be hard to read, below you’ll find the exact indicator and fault measurements along with what they mean.
Color Code: Red, Yellow / Orange & White (clear)
These are the colors you should see on the tester. Red is the most obvious of the colors, but yellow on the break down translates to orange on the tester. This happened because orange clashes with red and doesn’t show up as well. White or clear means that there should be no light at all.
Indicator Fault
0ff 0n 0ff Open Ground
0ff 0ff 0n Open Neutral
0ff 0ff 0ff Open Hot
0n 0ff 0n Hot/Ground Reversed
0n 0n 0ff Hot/Neutral Reversed
0ff 0n 0n Correct
Open Ground: This means that the ground wire is loose or has not been properly connected.
Open Neutral: This means that the neutral wire is loose or has not been properly connected.
Open Hot: This means that the hot wire is loose or has not been properly connected.
Hot / Ground Rev: This means that the ground and the hot wires are reversed or shorted somewhere in the circuit.
Hot / Neutral Rev: This means that the hot and neutral wires are reversed or shorted somewhere in the circuit.
Gardner Bender FAQ 
All three lights, 2 amber, 1 red, are lit. What does this mean?
Normally when you see this, the first thing that you will want to check is all of the connections on the back of the receptacle, and if all of those are tight, then the receptacle before that one on the circuit. Many times when you see this, there is a loose neutral connection on the receptacle. You will also want to make sure that you do not have any other appliances or electronic devices plugged in on the circuit. Sometimes components inside of these products can create feedback or leakage to another wire that will give these types of testers problems. Plugging into a 12V DC to 120V AC converter will also have this issue.
If none of these steps resolve the issue, then we recommend that a licensed professional examine the situation for you.