Some Adventists wear makeup and others do not. In the past the use of makeup has been discouraged due to teachings on modesty and simplicity of appearance. In general, it is up to the individual to decide whether or not to use makeup, though they might encounter some disapproval.
They can if they wish, though some may choose not to out of humility. Also, many Seventh-Day Adventists are vegetarian, and may avoid makeup as an extension of that. Nothing prohibits the practice, however.
Adventist women do wear makeup. It is not against the religion and this decision whether to wear makeup of not depends upon the sole individual and the immense faith the individual perceives by following this religion.