C code: "sizeof" will be as same color as background in light color scheme

[Jia-Rung (Tiba)]

C code: "sizeof" will be as same color as background in light color scheme.
It is not visible until cursor line make that line become grey.

Thanks

[André Müller]

A yes, I overlooked this one, since I mostly use dark colors in the terminal. The latest commit should fixed it.