River red gum finishes

I have several slabs of River red gum which are eight hundred years old. I use one slab for a desk suspended over 2 filing cabinets. I spent a long time sanding it to a fine finish. I found that the freshly sanded wood had a pale pink colour, but this oxidised rapidly, commencing within minutes of exposing the new surface, and developed a reddish colour. I finished this with a tung oil/laquer finish which further deepened the colour to a dark red. I would like to turn a second slab into a desk for my daughter, but want to retain the light pink colour. Any advice on how to achieve this and on what product to use to seal it.

Thanks

Albert