I have clients that worry about their roots coming through before they see me for their next appointment and I always give them a couple of pieces of advice.
If you can, find a root cover-up stick or similar sort of product. These are an effective way of masking the grey without actually colouring it and messing around with what your stylist has done. They can be purchased online and come in a variety of shades, I would always recommend you use a lighter tone rather than a darker one.
If this is not what you are looking for, I would ask whether your stylist would be able to tint your hairline and parting. I have a number of people who I do this for if they can't cope with seeing the white. This is a great way of keeping the greys at bay and shouldn't be too costly.
