When you colorize a photo, the colorized version is not added to your albums on MyHeritage as a new standalone photo. Instead, it piggybacks on the original black and white photo. This way it benefits from the same meta-data of the original photo: same title, date, place, people tagged, and so on.
After colorizing a photo, you’ll notice a colorization icon in the bottom right corner of the black and white version of the photo, in the photos section of the website.
These icons help you keep track of which photos you’ve colorized. Click the photo on the album page to open the photo page, and then you can toggle between the black and white and colorized versions. Your original photo remains intact, without anything added to it.
If you would like to have the colorized photos on your 'My Photos' page, you can download them and then upload them separately.