One tool that I use commonly is accessible-colors.com.
You can enter a foreground and background colour. It will tell you if they contrast well enough, and if not propose changes to foreground or background that would be more legible.
Enter #000000 for the black background. If you don't know what code the colour you want is Google has a colour picker that gives you the hex value on the right. Just copy and paste that in to accessible-colors.com.
If you're not sure what colour to start with and you need inspiration, try using colorsafe.co. Again, enter #000000 (black) for the background and it will propose colours that can do the trick.
Ideally you want to pass what's called AA level guideline for web accessibility. This will ensure that there's enough contrast between the text and background that users with low-vision problems can still read the website.