The colors look the same to me. The first letters of the words are capitalized in the new headers, though, which means that the first L shows more of the darker, bluer green than the old header's L did. That might be what you're noticing.
I checked and the text definitely has a different color. It's currently #538D4D, but something like #38A174 in the screenshots.
Design sketches
1. Notes on differences between these images and what we're planning on implementing:
2. Meetup widget in sidebar, listing the 5 nearest meetups occurring in the next 2 weeks, linking to:
(something like right-click & "Open Image in new tab" will help here)
3. New headers: