I am told the Citori line was factory coated with an epoxy. It would be dang tough or nearly impossible to blend the repair.
My 725 was a tinted clear ,hiding a beautiful piece of wood.
For a temporary, or cheap repair, you could mask off and fill the gouge, then paint it your favorite color
Kind of like a fake end cap ??
I'd try masking off the grip, just below the deepest part of the gouge and file it down flush then gradually sand/blend, only refinishing the grip cap area.
I think it'd be fun to try, I just refinished an old, beat up stock on my Dad's crackshot and thoroughly enjoyed the time spent on it. It had a similar gouge at the forward tip of the comb and now you'd never know it.
Those guns had a clear poly coating. Its probably starting to let loose and have some cracks. Best result would be to remove the coating repair the grip (easy enough) and do a oil in pore build up that will make the wood look 10,000 times better than what's on it now. The checkering can be chased and cleaned up as well. Its almost impossible to blend that original finishe as it has probably yellowed over the years.