I don't recommend coding complex expressions in EL. Even if you have vast quantities of experience and know how the EL process works from the inside out (I do), debugging EL is a major pair in the sit-down-place. Plus, people routinely abuse it to break the separation between Model and View in MVC.
What my little XML snippet is intended to portray is a situation where the backing bean has to determine which styles to apply to the control. It's a lot easier to code and debug JavaString expressions in a backing bean than it is in EL.
Also note that I used a style class instead of a brute-force style. That allows fine-tuning (and skinning!) the styling without requiring application code modifications, since only the CSS needs to be updated if you design the right set of style classes.
An IDE is no substitute for an Intelligent Developer.