wearing a color is a wonderful way to expose yourself to the benefits of
color therapy healing! you can also find jewelery made of stones/crystals with the same healing properties of the color you are using.
your exposure to a color depends on many factors like what you are trying to treat, the color that you are using, other health/mental/spiritual problems you may have in your life, as well as the type of color you are exposing yourself too.
for instance, it is very easy to "overdose" on red, if you need more red energy and choose to wear a small piece of red garnet, wearing it all day should not be a problem - but i would not recommend sleeping with it on. if you are staring at an entirely red screen for exposure, i would limit it too 1-5 minutes, again depending on what you are trying to treat.
all of these recommendations would be mute though if you had high blood pressure or were fighting inflammation, in which case i would NEVER recommend using red, and would use orange or yellow instead to treat a problem.
hope this helps!