I have always liked simple elegance. It would be my suggestion, and it is the brides choice, that the wedding dress be white not overly fancy with a sash over the shoulder. As she comes in to the church she has a Livingston sash over her shoulder. After the marriage is finalize and the husband kisses the bride the best man or ring bearer steps forward with a IPA sash. The new husband pins the IPA sash on to his new bride in a way to cover the Livingston.

This could signify his welcoming her into his family, and if done correctly hide the clash between the IPA and Livingston tartans. During the reception she could change into a Livingston skirt with a white blouse and a small IPA rosette on the shoulder. The rosette should be far enough away and small enough not to make the clashing tartans to bad.

Having said all this it should be noted that my wife has to coordinate my clothes or she will not let me out of the house.