If I omit a detail in a description that is known by the character but unknown by the reader because of circumstance, should I worry about it? Example: My MC knows the color of something because he's seen it before. When the MC encounters the thing during the story, it's too dark to know the color. I feel weird describing the color even though it's too dark to tell even though color is something that is often described. My instinct is to not worry about the color, but what are the common ways to deal with details such as this?