Many ways to aproach it, personally I would start with white, add green, slowly till it got close, then you will likely need some yellow, and if its to green looking but otherwise close, then use a drop of red to deaden the color slightly.
Its really hard to accuratly guess what it will take because the color density of each color can vary so wildly within a particular type of paint. Its much easier to darken a color than it is to lighten it. That is why i will generally start with the lightest color I anticipate using , and add the second most prominant color, ( green in this case) . I would anticipate perhaps needing a touch of brown, or like I said red to kill some of the "prettyness" of the color as it gets close. In paint tinting this is called clean, or dirty. this color is fairly clean.
the BEST way to approach this, is to mix up a small, as in one ounce batch to find out about how all the colors interact.
this way you can goof up several times and still not hurt anything.