I think the colors for the whole kit work well. The color of the plaid matches the kilt tartan well, and even though I can see it is the same tartan it is obviously a smaller size sett of the same tartan, which disturbs the visual for me a bit. Not sure why, because it is not unusual to see ties or caps of lighter weight and smaller sett but otherwise identical tartan put together in an outfit.

I think the other unbalancing effect for me is the use of the Argyll as a daytime casual sportcoat, like a man's blazer, rather than as dressy as I am accustomed to seeing it. Daytime casual still looks best to me with a tweed or a sweater. I think the Argyll is a bit strong for this use, personally. The plaid looks good with the Argyll but the Argyll looks a bit out of place. But I guess you would not be able to wear the plaid without the dress of the Argyll, so it is necessary if your goal is to wear the plaid out in daytime.

Just my tuppence.