you have two options. You can make sure your ViewModels aren't jagged. This is accomplished well by using the knockout mapping plugin against your model and having it use a constructor of your type. this way you can even define defaults
the other option is to reference the values off of the $data context. IE:
<div data-bind="style: { textAlign: $data.align, backgroundColor: $data.bgColor, fontFamily: $data.fontFamily, fontSize: $data.size, color: $data.color }, text: $data.title"></div>