Nothing will be perfect. Everyone adjusts thier screen differently. What you are seeing on your screen will be different than mine. SW has a setup that you can take a picture, upload to thier website and you can change colors but still not perfect.
Same with color swatches, you are looking at ink, not paint, they vary from one color deck to the next.
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Agreed, Sherwin WIlliams is probably the best, but due to your own settings on the computer/tablet/phone the colors will look different. Then, you have to take sheen into consideration...I think only contractors can get the big book thing that SW offers with all their colors linked together, but use the site to find a color family you like and then go get the little sample pages at the store. If you have Texas Farm Bureau insurance, you can get up to 30% off (look at the TFB website). Painted a LOT of houses inside and out and SW is all I use anymore.