@lblanco: Elaina is right. The typographic word for "bold text" is (letras) "negritas" or "negrillas", so nobody should be offended.
"Poner el texto en negritas/negrillas" is correct.
"Oscurecer el texto" would need some thinking before figuring out what you mean.
__________________
♪ ♫ ♪ Ain't it wonderful to be alive when the Rock'n'Roll plays... ♪ ♫ ♪
|