If there is yellowing in the fur itself, in natural sunlight, that can happen with age, diet, bedding, cleaning supplies used in/on the cage and even a hint of beige showing up. The yellowing or reddish tint fur can show, is also often due to oxidation. Fresh air constantly is a must. The closed doors and windows in the house often make the air you breath a lower quality of air than the air outside.
Did Sebastian loose the eye due to a fight/injury or because it was still closed when he was born and it atrophied?
When taking pictures of your chin, it is always best to do it in natural sunlight, without a camera flash, if possible.
Strong light, especially flashes, will 'bleach out' and discolor many things in a picture.
"Red eye" or those spooky white globe-eyes are a reflection caused by the flash.
Remember also, the dust bath dust reflects light, intensifying the reflection of the flash.
"Natural light" bulbs can also be purchased to use when taking pictures.
Never use fluorescent lighting in the same room as you are taking the pictures, it will give white fur a yellow cast and discolor other colors of fur.
Natural lighting will often give you a bluish tinge to pictures, if you are getting a greenish tint to your pictures, there is something yellowish that is crossing the light spectrum with the blue. (Notice the bottom left corner of the second picture.)
Always try to use a white background, if possible with all chins, except the white chinchillas ... with them, a black is usually best.
Any time you use any colors other than white or black for the background in your pictures, the colors around the chin can be reflected in the fur and give you an off color, rather than the natural color of the fur.
When using professional natural lighting ... If you use a reflecting shield or umbrella, it should be snow white or a high polished silver to keep the lighting natural.
Natural sunlight is always best, whenever possible.
When I do not use my light box, I will often use the dining room table placed closest to the window and covered with a white or black blanket for taking pictures. You want to make sure the blanket or background is one that absorbs light, not reflects it. 100% cotton that has been washed is usually best.
Do not use a white sheet, it is not thick enough ... any colors under the sheet will often 'bleed' through. ( I was a professional photographer for over 16 years.)
Hope these hints will help.
Jo Ann