Isn't there more than one run of xmaks tartan?
And, are they the exact same hue of blue?
If the tie was more of a neutral (Black, Grey, White) or contrasting color (Red,Yellow, Orange) with a stripe(s) in the xmarks colors wouldn't it be less likely to fight with the Kilt. It might even coordinate with other kilts better. Unless, of course, you are wanting to make this some kind of uniform look.