Question about Garmin fenix 3 Saphir HR Performer Bundle

Hello Lorb,
Basically, of course, it's all a matter of taste and very subjective.
The Fenix 3 HR has a dark grey / graphite-coloured housing, so I could personally imagine that the brown leather strap would fit quite well. For sports, however, I would recommend the strap that comes with the watch.
Many greetings & hope for the right decision
Matthias