Without greater context I recommend a simple ReplaceAll operation, to work on all appearances of Style at any level.

{1, Style[2, Red], 3, Style[4, Red]} /. Style[x_, ___] :> x

{1, 2, 3, 4}

If you want to strip Style from only numbers then you could use something like:

/. Style[x_?NumericQ, ___] :> x

Without greater context I recommend a simple ReplaceAll operation, to work on all appearances of Style at any level.

{1, Style[2, Red], 3, Style[4, Red]} /. Style[x_, ___] :> x

{1, 2, 3, 4}

If you want to strip Style from only numbers then you could use something like:

/. Style[x_?NumberQ, ___] :> x