Syntax highlighting for default parameters

[macgyver]

When function parameters are given a default value, it would be nice if these variables were highlighted as they would be outside of a function signature. Currently the entire parameter section is a single color.

I know this is in part dependent on the theme but I looked at a number of them and they all seem the same in this regard - is this a limitation in Sublime, or the themes I've checked, or is it something that could be fixed?