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Here is the relevant paragraph: 

Install Light-Colored Curtains 

Thick or dark curtains may be effective when you want to sleep or reduce the draft from your windows. But they’re not very effective when it comes to allowing more natural sunlight to come into your home and brightening up your living space. 

For your bedrooms, we recommend that you opt for black-out shades that can be easily rolled down in the evening before going to bed and rolled back up in the morning after waking up.  

As for your dining room, living room, and other areas of your home where people tend to gather, install light-colored curtains or blinds that can be easily retracted if necessary.