ui:define is not a GUI display element, it's a macro definition. So there's no style attached to it, only to whatever GUI content it expands into.
Technically, yes, you could define a macro and pass it a parameter which would be referenced in one or more of its expansion elements using an EL expression. In real life, I'd be more likely to pass a style name rather than hard-coding style values, however.
An IDE is no substitute for an Intelligent Developer.