Love it but bought wrong colour

I picked up Garnier express retouch at the local pharmacy. Since my grays come in faster between colourings I needed something to help me through a week or two before colouring. I like the application of this product, very easy , just dab the sponge applicator where you need colour. Works great along the hairline , no messy splotches in your face . My only problem, I bough dark brown instead of brown. Once I finish this I’ll get the right colour for me. Too bad no testers available in store .

Best I've tried

While this is not a totally perfect product, I will say it is hands-down the best product to do this that I've tried. I've previously tried a spray-brand of root cover and the experience was terrible and it stained my clothes. This is neat, applies well and has very few downsides, so let's talk through them now.

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Application
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Super simple, shake while upside down, sit right way up, open and apply. It's essentially 'sponging' the colour onto your hair. If you have shorter hair, it can be tricky to avoid getting it on skin, but if you do you simply need to wipe it quickly with a damp cloth or cotton pad and it will remove before it dries.

Just apply it to your hair, leave for 3 minutes (5 to be safe) and then brush through.

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Effectiveness
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It actually works really, really well. I have dark brown hair and my roots are threaded with grey and white. While it takes a little more application to cover the pure white hairs it does an amazing job on the grey ones. White hairs will shimmer a little more and will start to show through faster, but the grey's remain covered until you wash your hair.

Most important for me, it's not messy. When using a spray, it dripped all over my clothes, with this, it never goes anywhere but the sponge and is very easy to control. Furthermore, once it's dry, it's totally dry. That means if somebody touches your hair, it doesn't transfer to their fingers. When it does come off a little (if you rub it really hard), it's dark powder like flakes (like dust) rather than liquid stain.

Wearing it, it makes your hair a tiny bit stiff, it sort of feels like wearing extremely light-hold hairspray, but feels natural compared to other products like this I've tried. The colour is spot on and matches my dark brown hair perfectly.

It's very natural looking and probably the only problem I have with it is that after washing my hair, my hair still feels a little stiff and if I pick at the roots, I can still see a bit of the product there, so I wish it washed out a little easier.

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Summary
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Overall, it's the best product I've tried for covering roots, while it's not perfect, if I needed a product for this I'd definitely go with this one again.

Things they got right:
- Super simple to apply.
- Doesn't drip or stain clothes (and easy to wash off of face if you make a mistake)
- Covers grey perfectly and white pretty good.
- Dries completely and can be touched without staining.
- Doesn't make hair super stiff (feels like wearing a light hold hairspray)
- Colour fits dark brown perfectly

Things that won't suit everybody:
- Doesn't wash out easily (some remained even after washing).
- Instructions are only written on the box and not on the bottle (but it's pretty simple at least)