long time lurker first time poster - hello!

i’m currently knitting the camélia cardigan by knits pour moi and i’m on my third (and final) skein of the suggested bouclelaine in natural white for the button band. well it looks more cream than anything compared to the rest of the garment and i checked all skeins are from the same dye lot.

bouclelaine were surprised at this too and suggested washing the garment (i’m going to do the other button band and then the neck before washing it all anyway, but when i was comparing what was left of my second skein to my third skein i could see the difference).

i was wondering if that fails what are some ways to whiten wool? thank you!