Hi there.
The Galaxy S7 is set to "Adapt Display" by default and uses a very wide color gamut, which is wider than most content you'll see which is usually set to sRGB.
Until the S7 receives Oreo, automatic per-app color management is not available, but you can set the preferred gamut type to sRGB manually.
1) Open "Settings"
2) Tap "Display"
3) Then, tap "Screen Mode"
4) From there, select "Basic"
This tells the phone to use a gamut more akin to sRGB. The colors will be significantly more muted in comparison but should give a more accurate picture to what the content was originally created on.