the mortar wash isn't meant to stain bricks. (it won't be absorbed) it's meant to cover or 'wash' it.

if you want to 'stain' or change the brick color, they do have brick stain or a special masonry paint/lime wash

lets see the fireplace you want to change

Thank you. I am looking for a solution to soften the new orange brick we used. It is mixed with old brick we had and I am trying to tone it down and make it cohesive. Maybe some sort of light wash? Thank you for any advice.

ah, I see.

they do have concrete stains/tints. I'd prob tint the lighter ones as close as possible to the new ones. (if that's the color you want.)

You may have to mix a few colors to get as close as you can to the orange. and you may have to apply a stain to the new brick, just so they all match w/the same texture and finish.

DyeBrick stain

https://www.dyebrick.com

or, you could see about doing a concrete stain. not sure what it would be like on clay brick. you'd have to do some samples. (and you'll prob have to mix colors/stains w/this product too. you aren't going to find a pre-made exact color-match)

Behr has this brick/masonry stain/paint you could have tinted any color

https://www.homedepot.com/p/BEHR-1-gal-SC-533-Cedar-Naturaltone-Flat-Interior-Exterior-Masonry-Stucco-and-Brick-Paint-27201/302143346

https://directcolors.com/diy/stain-concrete-brick-pavers

DirectColors, above, has products.

even SW has brick stain

Plenty of options for you!

if you can't match exactly, but get close, you could then go over all of them w/one type of lime wash.

https://notinggrace.com/how-to-install-and-mortar-wash-a-herringbone-brick-patio/

https://redeeminghampton.com/free-diy-white-washed-patio/

Thank you so much for all that information. I do not like the orange color and would love to make it more neutral or more antiqued like the original brick which is less yellow. I am wondering if a light mortar wash with grey might tone it down?