The first latches were black but were changed to tan sometime before 2012-2013 from what I recall. (This is not official, just observational based on following SCARs in this thread and getting mine---both tan latches---that I got in 2013).
My understanding is that they addressed shortcomings with the stock latches failing. Not sure why they decided to change the color other than matchy matchy.
You might see TangoDown
aluminum latches on some guns, which are also black. Though these may have fallen out of favor because the interaction between an aluminum latch and plastic stock could weaken the plastic over time.
You could probably get an idea of when the change occurred by going through the SCAR picture thread from the beginning and noting latch colors and post dates.