This took a little digging through the documentation, but I did find it...
This example will give red font to all of the selected cells.
callback: function (key, options) {
var cell = $("#dataBlock'. $val['id'] .'").handsontable(\'getSelected\');
var startRow = cell[0];
var startCol = cell[1];
var endRow = cell[2];
var endCol = cell[3];
if (key === "redFont") {
setTimeout(function () {
curRow = startRow;
curCol = startCol;
while(curRow <= endRow){
curCol = startCol;
while(curCol <= endCol){
check = $("#dataBlock'. $val['id'] .'").handsontable("getCell", curRow, curCol);
check.style.color = "red";
curCol += 1;
}
curRow += 1;
}
}, 100);
}
}