Question On front panel header, how can I tell which is the positive connector and which is negative?

What board are you working with and what case? For the most part, on the front panel, it almost doesn't matter. Switches don't usually care which direction power is flowing and mostly LEDs don't either. Still, it's best to get the polarity correct whenever possible.

"a little arrow on the back" of WHAT?
 
The motherboard manual will have a diagram.
Orient yourself via the space with no pin.

The front panel case lead will often have a + on the positive lead.
+ is usually the colored wire, and ground will be the common(black/white) lead.
It does not matter for pwr and rs switches.
For led leads, the led will simply not light up if you have it backwards.
Just switch it.
 
Aug 26, 2022
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Thank you. The manual only specified the one wire specifically that was positive or negative with the other cables having a small arrow on one side. From what I've found, it seems the arrow is meant to represent the positive.