One suggestion would be a couple pairs of "go to" hose that will do you stead in almost any situation even as your kilt collection grows and blossoms new color combination confusion. A nice Charcoal grey goes with nearly every thing, as does a nice claret red, although they go better with some than others. Many feel black goes with anything but I disagree as it seems too strong and dark a color for many tartans, hence the charcoal which softens that darkness a bit. There is always the perennial natural or "ecru" kilt hose (not bleach bright white) which also look fine with everything but not especially great with anything. As you venture into other opportunities to add to your hose collection look at the secondary colors in your kilt/s, be they navy blue, tartan green, lovat blue, lovat green, ancient blue, even brighter red or yellow or orange, etc... for accent coloration possibilities, or stick with your standby standards and choose these secondary colors for your flashes and other accessories in you attire such as ties or shirts. Most feel that red or claret flashes look good with just about any hose and just about any tartan, within reason.

As Chas says above there are several ways to make flashes and garters in a variety of colors as well as from tartan remnants if you have any from your kilt build. A couple pairs of "go to" hose and a variety of complimentary flashes should stead you well for a long time, at least till you can either afford more or can decide which others you might want to try. Look at lots of pictures here on X. If you find someone whose style fits yours, or who may have the same tartan kilt as you, look in their personal photo albums (if they are public) or for photo posts by them in the forum threads or gallery to get some ideas how others deal with the hose and flashes as they relate to your specific tartan, and how folks do it in general. Everybody is a little bit different but some generalities arise over time for most of us. Or just graze the gallery or the "Give us your best kilt picture" thread for some ideas. Lots of great examples to be found just with a little focussed grazing.

Not having a Black Stewart I am not personally aware of the specific colors in the tartan but I assume black, white, red and at least some green, and a couple more minor colors like yellow and possibly some blue. I imagine one could wear black or charcoal or red hose with impunity, and look for complimentary flashes to set off the hose from the group of minor colors in the set. I would personally not wear black flashes unless with a much lighter hose (red, yellow or ecru) or unless going to a funeral, far less likely to a wedding unless it was part of the wedding party attire. When I wear tartan flashes I tend to roll them up once to shorten the amount of tartan that hangs below the hose cuff turnover so it really is only a little flash of tartan (maybe an inch at most) rather than a pair of long ribbons of tartan hanging off each calf below the turnover cuff. Still provides the desired flash but less of the kilt shop mannequin appearence look, especially realizing that flashes are really an option rather than a necessity.

I like Chas's ideas for generating a broad variety of flash color options in a very inexpensive way. You can also buy sets of color flashes that come with a single pair of garters and simply swap out the flashes onto the garters at will---I have two sets, one in modern colors (tartan blue, bright gold/yellow, bright red, and tartan green) as well as a second in ancient or muted colors (rust, a faded yellow, ancient blue, and almost lovat green) to compliment a few other frestanding colors like grey, as well as my tartan flashes and a few mixed color garter ties.

Good luck in your choices. Pictures or it didn't happen.