Stats preview card component - mobile first

I just completed my first project here and it is ready for review. I would greatly appreciate any feedback on the image header overlay. I have never done an overlay before and to me it looks like the color of the overlay isn't quite the same as the design preview. I'm wondering if there is another technique for doing overlays, as I just used HSLA colors to adjust the opacity. I would also like to know how I could center the .container on the page when it reaches a screen size of 768px.

If you can also tell me if there are things I need to improve in my code I would really appreciate it.