However, like most rules of fashion, it is permissable to bend or break this one so long as the general principles are understood. I have, within the past recent months, acquired for myself a black casual kilt belt and simple black leather sporran, and have been occassionaly wearing them as part of my daily dress with great success.
Some of the kilts in my wardrobe, I concluded, would look better -- even in casual wear -- with black leatehr accessories. For instance, one of my kilts is the Mull tartan, which has a large black stripe as one of the pivots. The other two colors in the tartan (green and azure) are both rather light, so the dark black really stands out as a visual feature of this kilt. Another kilt I have is modern Armstrong. The main colors of this tartan are black, dark green, and navy blue. A red stripe is the only bright feature of this otherwise dark tartan. I also have a kilt in a dark charcoal grey Harris tweed. While brown leather looks fine with any of these kilts (especially a darker brown on the dark green of the Armstrong), I couldn't help but think how nice black leather would go with all three of these.
So now I have in my wardrobe a black leather sporran, belt, and sporran strap as seen in the picture at right (worn here with the Moffat tartan). These work great, in my opinion, for casual daily wear. And they also allow me to wear certain accessories that I wouldn't otherwise with my brown sporran and belt. For instance, I now have a pair of black garter flashes that look stunning worn on either lovat blue or green hose with my Mull kilt. I have a lovely black casual short sleeve button shirt that goes great with many of my kilts, but matches the black leather much more than the brown.
When selecting black accessories for casual wear, here are some guidelines to keep in mind. You are looking for casual wear and not formal wear. Black is the color for formal wear and so a lot of the black leather accessories being sold will be for formal wear. I would avoid what is marketed as the standard kilt belt (black leather kilt belt with a separate rectangular buckle, usually nickel plated). This is the style seen most often worn with the kilt (the top belt on this page, and the buckles shown beneath it are examples of what I am talking about). You'll find that this is the most common style of belt seen at Highland Games, worn even with very casual wear. I've seen this style of belt worn frequently with t-shirts and other ultra-casual wear. So if this is the only belt you have, you won't be out of place wearing it to the Highland Games or other Scottish festival. Still, I'd like to see this style belt reserved for more formal occasions.
For casual wear, a belt like I am wearing above (listed as a "clansman" kilt belt on our gift shop page) is more suitable. Something with a traditional buckle like this is ideal. A lot of belts sold for re-enactors, colonial era, Revolutionary War, and the like, will work for this purpose.
As far as sporrans go, something simple and plain like you see above is what to look for. Any of the ones shown on this page will work. For daily wear, you don't want fur, silver, or anything flashy. Some ornamentation is fine, but don't go over the top. The simpler sporrans shown on this page will work fine for casual wear, but keep it as simple as possible.
Some fur might be ok, so long as the rest of the sporran is simple, like this model:
Likewise, some silver decoration might be fine, so long as it does not go over the top. The below one would be acceptable, in my opinion:
This one, however, I would deem too much for casual wear:
And sporrans like the ones listed here (example below) are strictly designed with formal wear in mind.
Little things like wearing an all leather black sporran belt instead of the more usual chain also help to keep the overall look of the outfit toned down, and thus more suited for daily wear. And that is the goal in casual Highland attire. Keep it neat. Keep it simple. Keep it understated.