The word dusky is used as an adjective for dusk which means the time of the day when the sun is almost set but light is still there. The period can neither be called as of dark nor of full light but the period that falls in between.
When you are using the term 'dusky', most of the times you are conveying a figurative message and can be said to be a colour that is not very bright but soft. The word can be used for any shade of colour when it is not very bright. Sometimes people use the term to describe the colour of a person's skin. If you find a woman who is not very fair but looks very charming you can use the term 'a dusky beauty' for her.
When you are using the term 'dusky', most of the times you are conveying a figurative message and can be said to be a colour that is not very bright but soft. The word can be used for any shade of colour when it is not very bright. Sometimes people use the term to describe the colour of a person's skin. If you find a woman who is not very fair but looks very charming you can use the term 'a dusky beauty' for her.