My images loose quality because colors are removed.

The color reduction occurs when you save your animation. This is because a GIF animation can only contain 256 colors, no more – this is a limitation of the GIF file format specification.

There are several things that may help:

• Before saving your animation, on the Animation Properties tab, enable Do not merge pallettes. This will increase both the quality and the file size of your animation.
• You can try changing the Dithering Mode. On the Tools menu, click Options and then select Import tab where you have two choices. Floyd Steinberg is usually the best option.