After recent highlights, my hair has gone a bit brassy. It's unusual as it's the same I've had done for years. Perhaps they were left a little too long this time around and I just find it way too warm for my linking
Bit confused. Do you have blonde or light brown highlights? Might help if you describe your natural hair colour and then what shade your highlights are.
Assuming we're talking about blonde highlights, if your highlights were left in longer (assuming you mean the bleaching stage), your hair would be brighter and less brassy as you've lifted past the orange stage.
Did the hairdresser apply any toner/dye afterwards? Was it a semi or permanent toner/dye?
Toner is usually a demi or semi permanent dye applied after bleaching hair to enahnce or correct the colour. It does not lift the hair and it only deposits colour. In theory it will not damage your hair, but if your hair is already damaged it could exacerbate the damage or lead to an unexpected colour result. They only last 6 - 12 washes so need to be maintained.
To be honest, if you've had a semi/demi dye applied you can apply a toner at home. If you've had permanent then I would go back to your hairdresser as applying other dyes over the top of perm dyes can lead to disasters.
Purple shampoo only works on yellow blonde hair so if yours is brown or orangey it won't have much affect. It's worth a go if you want a cheap harmless option.
Again, assuming blonde highlights are the goal - if you do want to tone at home, maybe look at the Josh Wood Shade Shot in Icy Blonde. It's a semi dye applied like a mask so should give a bit of colour correction along with nourishment for the hair. You'll need to patch test first though.