Testing the pH of bar soap isn't really necessary. It doesn't tell you whether the soap is lye heavy or not, which is the real question that most soapers are trying to answer when they test pH. If you really want to test your soap's pH, you can use a pH meter. But again, it doesn't answer the question about excess lye. That is best done via the zap test.
Also, pH strips are notoriously inaccurate, usually on the low side by several points. Your question illustrates the point perfectly. Results in the green zone would indicate pH around 6, which is scientifically impossible for bar soap. Below ~8 pH, it will cease to be bar soap and will separate. Anyone who claims their soap is at 6 pH is either ignorant, or a scammer.