Oh no, I just realized something else.
In my lab manual it listed the colors of ions in solution. I choose copper, iron, chromium, and nickel as my cations because they are under the green category. Remember, the unknown substance is a green powder.
However, when it completely dissolved in the HCl, NO3, and 6M NH3, the solution was colorless. It was not a green solution or any other color. But of course when the substance did not dissolve in the H2O and NaOH, the substance remained green in the solution and gave the solution a green tint before collecting at the bottom of the test tube.
Should I be looking at the cations listed under "colorless in solution" rather than the green ones? If so, that would really suck because the possible cations behave that way are: silver, lead, bismuth, antimony 3 and 5, tin 2 and 4, aluminum, and zinc. I really hope this isn't the case.