Renovating wood staircase - Issue with different wood tones

[Aljames]

Hi, I am trying to renovate staircase so that treads are varnished (natural wood) and the risers will be painted white. There is a visible line where a previous carpet must have been. Have spent about 20 minutes continuously sanding the bottom step which is just about acceptable but will be labour intensive and create loads of dust to do the lot. Are there any other methods of removing the stain / recommended sanders / methods of matching the two wood colours. Have tried dying the outer edges with stain and even tea to try and match the centre panel but still the tread lines are visible. Please see pic. Any advice appreciated as not sure whether it's a lost cause. Thanks

 

[footprints]

It's not really staining, its bleaching of the outer edges from daylight where in the past a stair runner has been fitted.
I don't know a proper answer but it might be worth looking at some method of bleaching the center rather than staining the outer strip.

I guess in time the stair will even out to some extent but I reckon it might be a long wait for a natural effect