iMessage uses shading based on transport (SMS/MMS vs. iMessage) for both your messages and others, but from looking at my own mixed SMS/MMS/Hangouts threads, Google uses green for your outbound messages sent with Hangouts, and grey for your outbound SMS/MMS messages and all incoming messages (with "via SMS" and "via MMS" alongside the time display on in- and out-bound SMS/MMS messages.)
So, to the extent that the Apple behavior can be seen as signalling in-group membership with color of messages, it is distinctly different from Google Hangouts, since the only person whose messages are colored to indicate delivery method in Hangouts are yours, not the ones you receive from others.
So, to the extent that the Apple behavior can be seen as signalling in-group membership with color of messages, it is distinctly different from Google Hangouts, since the only person whose messages are colored to indicate delivery method in Hangouts are yours, not the ones you receive from others.