The color options allow you to convert your files to Black and White or Color images. You can also select the Optimize option, which creates the outputted image using the minimum amount of required colors (based on the number of colors in the original file). The optimizing option increases conversion time, but may result in a smaller outputted file. Image quality is not affected.
When converting to black and white, you can enable the Use built-in black and white support checkbox to reduce memory consumption and speed up the conversion process, however use of this feature may negatively affect image quality.