Most cleaning products I am aware of could darken very light leather.
You could try some clear glycerin soap in a small area that is partially hidden, whether or not it darkens will depend on the leather and how it was originally processed and conditioned from the manufacturer.
If the test area darkens, the other solution would be to wipe all the mold off with a dry cloth, using disposable gloves and throw the cloth away after this.
Then use Lexol Non-Darkening Formula, even with the Lexol it might darken very slightly, just make sure you do not leave the Saddle in the sun to dry.
Many cleaners, conditioners or protectant when still wet on leather, have a chance of making the leather darker when leaving it in the sun to dry.
May all your Trails be happy and safe ones