Is there a way using iTerm2 to give the active tab more contrast compared to the rest of the tabs?

Yes, you can choose a Tab Style in the preferences, under the "Appearance" pane.
The standard styles "Metal" and "Unified" appear to offer better contrast for the active tab than the other two. From your screenshot, it appears you have selected "Adium" which does indeed have very poor contrast.

One workaround I found is to set the tab color to a pale and greyish color e.g. 47736b in Profile->Colors->Tab Color and have Light High Contrast theme active. The active tab will have a light bright color.