It's hard to have the perfect color and contrast since the background has almost every color possible!
But you can add some effects behind your text to light it up or to make it darker, and play with the contrast this way. That lets you also some freedom to use another accent color... Eg. the color of the logo of the business that website is created for.
You can't do all these effects with CSS, both some of them yes. I did these with Photoshop and used the layer style (double click on the layers with your text to see them.)
Here is an example with a transparent white box:
Here is an example with a transparent full width white box:
Here is an example with a transparent full width black box:
Here is an example with a large drop shadow and a box:
Here is an example with a glow and a box:
There's many options for that kind of projects but maybe these examples will give you some ideas!
If you only want to use text and nothing else, then you should choose the boldest font you can find, and if possible add a black outline or something around it.