The five Auto buttons which are located at the top right of the ColorWasher window let you perform an automatic color correction when clicking on them. This is a quick and easy way to color correct your photos. Each button has its advantages and disadvantages. So you should try all five Auto buttons before you decide which one achieves the best result for the current photo.
You can use the Auto buttons as a first start and edit the measured colors with the color boxes and sliders. But you can also use them if drawing a sample area on the preview doesn't achieve suitable results, because there is no gray or white area present in the image.
Nevertheless a good sample area usually produces a more accurate color correction than the Auto buttons. So if you want a perfect color cast removal, try drawing a sample area firstly.
Auto1 - "The Generalist"
The Auto1 button works properly on color casts that are visible throughout the image. That's because Auto1 analyses the whole image data for detecting a color cast.
Auto 2 - "The Wise"
Auto2 does a good job on images which are not too bright and not too dark. It analyses the midtones of the image to detect a color cast. Auto2 also works well on less obvious color casts. Together with Auto1 it works fine on most photos.
Auto3 - "The Illuminator"
Auto3 might work better than the other Auto buttons in some cases (e.g. when a white T-shirt or dress is visible in the photo). It is specialized on analyzing the highlights of images. So it should work fine on very bright images that aren't overexposed. Using Auto3 on images with overexposed areas often produces a less good result.
Auto4 - "The Combinator"
Auto 4 combines results of Auto1, Auto2 and Auto3.
That means if two of the three work fine, Auto4 will work very good. While it
works fine on many images it often doesn't work as good as one of the first
three Auto buttons alone.
Auto5 - "The Smurf"
The Auto5 button is a very special case. We noticed that the other three Auto buttons didn't detect certain blue casts, so we decided to develop the Auto5 algorithm. It is basically a mixture of Auto1 and Auto2, but is less effective on most images than these. Auto5 can fail miserably on some images, but it might do wonders on strong blue casted or otherwise difficult images.