It is not permissible in Islam for men to wear anything made of gold, whether it is a watch, a ring or anything else. For more, please see the detailed answer.

There is nothing wrong with using mascara because it is a kind of permissible adornment like kohl, but that is on condition that one does not appear wearing it in front of non-mahram men.

It is permissible to dye hair any colour apart from black, and there is no differentiation in this regard between old men and young men. So, it is halal to dye your hair red and yellow, but there are some guidelines to keep in mind, such as not imitating people who are evil and disbelievers. Please read below for details.