Style
Wolfram Kernel
Execution environment
Styling box used as a decoration for an arbitrary Wolfram Expressions
Style[expr_, opts__]
info
Expressions are editable
The argument opts contains directives for the formatted output.
Options
BackgroundFontFamilyFontSize
Directives
_Integerfont size_RGBColorfont colorBoldItalic
Example
Style[1, Background->Yellow]

For pure string options are much richer
Style["ddd", Background->LightBlue, FontFamily->"Monospace", Bold, Red, Italic, 20]

Hamlet's soliloquy, with repeated words successively has more contrast background
With[{data = ExampleData[{"Text", "ToBeOrNotToBe"}, "Words"]},
Take[MapIndexed[Style[#, 4 Count[Take[data, First[#2]], #]] &, data], 100]
]

Or for a regular expressions
Style[(*FB[*)((1)(*,*)/(*,*)((*SqB[*)Sqrt[2](*]SqB*)))(*]FB*), 18, Red]
