You can find out by using a browser extension such as Firebug or Web Inspector, or by looking at the CSS of the theme in Appearance > Custom Design > CSS.
Most of the text elements in this theme use Helvetica Neue (regular, light, or bold).
Which color are you referring to?
Thank you so much, that’s just what I need. I was referring to the colour of the text (because when I use black it looks much darker than what is just there, so I thought it must be gray – but now I will just find out).
I asked about the color because the theme also features a colored menu bar and a colored footer, so I wasn’t sure which color you meant.
The text color in this theme is defined as pure black (#000) but with 70% opacity (so it appears as grey). If you can’t reproduce that, the result is #4c4c4c.