As you already know by now, darker colors are usually better at blocking out UV rays compared to lighter ones. For this reason, you have a smaller chance to get sunburns when wearing a black t-shirt compared to an untreated white one. This goes for other colors too. If your clothing is pale, it will let through more rays. Some strongly colored dyes are very efficient in giving clothes the UVR protection needed.
Chemicals used on clothing don’t always have to be colored. The technology advancement has made it possible to treat clothing and change its characteristics while color remains the same. For this reason you have vibrant colored clothes of all types which is also excellent at protecting your skin. To wrap up, the best sun protection clothing to wear is treated and with a high UPF rating, but if that isn’t available for you then opt for darker, heavier and denser clothing.