Which type of product is typically used for neutralizing unwanted yellow tones in blonde hair?

The correct choice is toner, which is specifically formulated to neutralize unwanted hues in the hair, particularly yellow tones that can often appear in blonde hair. Toners contain violet or blue pigments, which effectively counteract yellow tones on the color wheel, providing a cooler, more balanced hue to blonde hair.

This is essential for maintaining a desirable blonde shade after lightening processes, as brassiness can occur due to various factors like environmental exposure or the natural warmth of hair. By using a toner, stylists can achieve a more refined look that aligns with the client's desired blonde tone.

The other options do serve different purposes: color correctors may adjust hair tone but are broader in application, deep conditioners focus on hair hydration and repair rather than color correction, and hair serums primarily provide shine and manageability without addressing color issues. Thus, toner is the most appropriate choice for neutralizing yellow tones in blonde hair.