Problem is if select element has options with same "text" but different values, in edit form select element's selected value is set wrong. I think selected value of the element is constructed by cell's text, not value.
I tried like this,
....
formatter:'select',
edittype:'select',
editoptions{value:"1:Blue;2:Red;3:Green;4:Blue"}
....
If selected item is value=1, when open edit form value=4 may be selected.