Unfortunately, as you have discovered, JuiceboxBuilder-Pro does not retain metadata (such as ICC color profiles) in images that have been processed (either resized or watermarked) for use in a gallery.
In order to have metadata in gallery images, you could prepare (and resize if necesary) the images for your gallery in Adobe Photoshop (or a similar imaging program) prior to feeding them to JuiceboxBuilder-Pro and deselect the 'Resize Images' and 'Use Watermark' checkboxes on the 'Images' tab. JuiceboxBuilder-Pro will then just copy the images directly across to the gallery's 'images' folder (complete with any metadata that they may have embedded within them) without processing them at all.
When the images are displayed in the gallery, they are displayed using regular HTML <img> tags (generated dynamically by the 'juicebox.js' file).
Incidentally, JuiceboxBuilder-Pro does not intentionally strip out the metadata. It is a side-effect of the way that images are resized. In resizing an image, a new image is created from the original image's pixels (using a suitable algorithm) and the metadata is not actually part of the process. In order to retain metadata, it would likely be necessary to extract all metadata from the source image, store it somewhere temporarily and embed it into the resized image. With all the different metadata formats available (e.g. EXIF, IPTC, XMP, ICC) and all their possible values, this is likely to be quite a complex task (and I do not know if this is even possible within an Adobe AIR application such as JuiceboxBuilder-Pro).
I hope this at least sheds some light on what is happening.
Processing images prior to using JuiceboxBuilder-Pro and instructing JuiceboxBuilder-Pro to use these images for the gallery (without any further processing) would be the best workaround at present.