Color for an uneven base

I had and have the same Problem. I tried a diluted (!) SFX cupcake pink and crazy color lavender for touch ups. It worked, was kinda light cool pink. I also used silver shampoo & conditioner, as the orange would get nasty after 2 days without washing. But this is always the problem with pastels, at least with me.

You could dilute a darker pink such as directions rose red. It's a cool purple toned pink colour and is highly pigmented so you'd only have to use a really small amount to get a pale colour.. I have found it quite forgiving even diluted.

To disguise the unevenness I would go for a gradient. Three colours such as liac/pink/peach will hide any banding.

To disguise the unevenness I would go for a gradient. Three colours such as liac/pink/peach will hide any banding.

How would I apply that?

Put the top colour on first, then blend where it meets the second colour. Some people make a mix of the first and second colour to make an intermediate colour to apply where the colours meet, it is up to you. The secret is good blending, I do it with my hands and just squidge the colours together.