Titanium rush / dark ash metallic is a dynamic color. Rather than a basic dark gray, it shifts color depending on the light. Like you, I was unsure about it and went to view it in person before deciding to order it.
First time seeing it was in the middle of the day with partly cloudy skies and I mistook it for black, thought the salesman was crazy walking me over to two black trucks but one was dark ash. Looked very dark gray up close and could see the difference with the black truck next to it. Looked at another one during a sunny late afternoon with the sun just starting to turn orange and you could see more of the purple shade come through but my wife just saw it as a grayish tone.
I’ve seen a few Escalades, trucks, and other vehicles with this color and depending on how the light is hitting it or the time of day, it mainly seems like dark gray or black. Like the picture above, the color has a lot of variance based on the body lines and the light where you can see black, dark gray, slate blue / dark blue, and some purple but never straight up purple.
You need to see it in person for yourself, you will see blue metal flake when viewing close up.