Hola
Pubic hairs going white are not a common occurrence.
However hair growing prematurely grey are referred to as Canities.
Genetic predispositions, Stress, Damage by cosmetic products used etc may all have a role to play and a more detailed history is required and the treatment tailor made for an individual.
Trust this info helps you.
Next Steps
Don't stress over it.
Contact a Dermatologist nearest you in-person or even Online if that suits you better for discretion.
Health Tips
Keeping the Bikini line clean shaven or going in for Laser treatment to do so may be a useful option/solution.