Code green usually means the fit is okay. However, it does not hurt to check whether Mx has really found a maximum (or minimal ?2ll), by adding option th = 4. Mx will then refit 4 times starting from the previous solution. If the ?2ll does not change, you probably already have the best ML estimate. If the ?2ll does change, the lowest value is preferred, and you must try to change starting values that will generate this optimal fit in order to compare nested models.
With a code green you can also add ?option jiggle? to check whether Mx has the found most optimal ML estimates.