What do you think a good contrasting colour might be against this tartan?
Why not a Lovat green? It's not necessarily "contrasting" (if by contrasting, you mean absolutely screaming "I'm the diametric opposite of what you see above me"), but it's definitely a color that's not represented in the tartan. I think it would look nice and traditional.

Even better, a darker shade of brown.

Now then chaps you are beginning to worry me-----again! I am reading in this thread, disturbing comments like;"a little more dressy" and " this or that colour is not very flattering" and so on. Before long you will start talking about "matching" again! Not that any of this is earth shatteringly important, but I do think you are tending to put too much thought into your colour choice. Wear any colour you like(apart from white) and wear the first pair of hose, of any colour, that come to hand when getting togged up and get on with life!
I certainly cannot argue with you from the standpoint of "what the Scots do". I was simply stating my opinion on what looks good. And while I have learned to embrace, even enjoy the Scottish art of not matching, I still have hangups on putting certain colors in certain places. With the exception of traditional diced/Argyll/tartan hose that look "right" with the kilt, I just can't get past the notion that loud socks are cartoonish. It's just my personal sense of style, I suppose.

But on the subject, are loud solid-colored hose traditional? I am, of course, aware that patterned hose have been around in Scottish tradition for as long as they've been wearing hose, but off the top of my head, I can't think of any early examples of solid-colored hose that are in bright colors like red, yellow, purple, etc. When did this trend arrive on the scene, as it were?

I though I really wanted a pair of ancient red hose, but none of the 22 girls surveyed in my office thought it would work for me.
This. Listen to the women. They are why we dress to look good, even if we won't admit it! If the women don't fancy it, just say no!