Are we talking "Cheap Yellow Mustard" or a Dijon variety?

Here is a picture of my old kitchen, which had an underpaint of an almost green/yellow mustard tone:

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The color was called fresh pear, but really was a pretty bright yellow with that new pear green tint. It looked wonderful with a dry brush glaze of burnt umber, then the second glaze was buff (or a white) again dry brushed on. (A picture of the kitchen base paint): {{!gwi}}

I loved this color and it was so much prettier when the glaze was on than when it was just paint.

This next room (dining room that flowed from the kitchen) was truely "Cheap Yellow Mustard" but then it had a gold glaze and a buff glaze, both dry brushed on over the mustard. It's great for a dining room, but the gold is a bit fancy for a kitchen. I just wanted to show you both. For examples of dry brush.

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The original of the dining room color: (without dry brush...on the plain wall) {{!gwi}}

This gives you an idea what dry brushing on glaze can do for you. I purchased my glazes at Home Despot (I like that brand glaze better...don't have a bottle here to show you though). Buy a dry brush and do one layer one weekend and one the next, (it comes out better if you let it rest between layers). The burnt umber and buff gives a perfect tuscan finish. And all of this can be done for about $30 with the cost of the brush :) VERY EASY!!!!

It may be easier to just repaint the two walls of mustard yellow in a shade that you like better. I'm not saying a glaze won't work, but it's not your only option.

In my last home we did ALL the living/kitchen walls a mustard color. I did, however, do a colorwash glaze over the whole thing which gave some texture to the color and didn't seem so...Mustard-y. Colorwashing is VERY easy. I used a HUGE wide brush and simply "washed" the walls with the slightly darker glaze. I'll try to find a picture if you're interested.

As for an accent to break up the mustard, we used a deep burgandy. Our countertops were dark black/flecked. Our backsplash was a custom mosaic of jewel toned tiles in a swirly pattern. We had natural maple cabinetry. I seriously need to post pictures! :)

Ok, uploaded some pictures. Click through and you'll see some of our mustard walls.

Here is a link that might be useful: My Mustard walls