e-man2: The 'Which colour if...?' questions have been covered many times before. There is also an explaination
here which may explain things a bit better.
If there is PMA mixed with an MDMA substance, then robadope will tell you that there is more than just MDMA. With such a prolific amount of pills out there if Robadope reacts then just throw it away and get one that doesn't react.
The main purpose of the test kits are not for you to find what you want, but to find things you don't want. That may sound like I'm saying the same thing, but there is a different emphasis.
If you are getting a purple->black with marquis, then a blue reaction with Simons, then 99.99% of the time you would be getting MDMA and NOT MDE. If you are not getting the same wooshy feelings as when you first started taking pills, then you may wish to give yourself a break for a while and just admit to yourself that the honeymoon is over.
To answer your colour directions explicitly:
MDA + PMA will turn purple->black with Marquis
MDA + PMA will NOT react with Simons
MAA + PMA WILL react with Robadope
The chances of getting a MDA+PMA pill are extremely slim. For maximum safety you should not take this pill. Of course, most likely you will be getting MDA by itself with such a test reaction
MDxx + speed will turn purple->black with marquis. The MD reaction will overide the speed reaction.
...to answer for Mayday: Of course the test kit may save your life! There is no guarentee of course, in this world there are very few absolutes. I've seen plenty of pills thrown away because because of a unwanted test reaction.