The sidebar in the new version is different. If you really cannot live without the old arrangement, you can always grab one of the older versions from here. They should work on Windows 8 without problems.
The sidebar was changed, because many people had problems with the old one. It was a bit overcrowded on smaller displays and some people did not figure out that it can be dragged up and down. Hence the tabbed design. The color palette is temporarily out, because in some cases, it does not fit in conceptually. When you are for example drawing a rectangle filled with gradient, the old color palette window would not make sense, because a color gradient uses more than 1 color. It may return in the future, but it will be a more general thing covering favorite fill-styles, not just favorite colors. The current color picker should be able to meet your needs. It has a separate hue selector - the circle - and you can then select more or less saturated or bright variations using the popup button or using the arrow keys.