About a week ago, I repaired a mortar joint between two bricks that had deteriorated. I spent several weeks trying to match the color by creating samples of mortar by mixing a mortar pre-mix with charcoal concrete coloring to get a specific shade of grey. Once I was happy with the color match, I went ahead and mixed up a small batch, but instead of using water, I used an acrylic admixture in place of water to be sure the new mortar bonds well. Well, it's been a week now, and the mortar has yet to lighten up from what currently looks nearly the same color as the wet mix! The mortar is dry and hard to the touch but looks to be nearly the same color as the wet mixture! I've never had this issue before. It is winter time, but it hasn't been freezing down here in the south. The temperature hasn't really gotten over 50 farenheit though so could that be the reason the color is still dark???? Any thoughts are appreciated!