In case you can't upload images when using Color Swatches Pro extension, please, get acquainted with the following potential reasons:
1. There is no write permissions on the "media/amconf" folder.
2. Make sure that you have pressed the “Update Images” button.
3. The server configuration max_file_upload prevents image uploading.
This occurs when attribute have many options and you try to upload the last one. To resolve the problem you need either increase the limit or upload images not more than about 10 at once starting with the first one.