I Need a Work Dress

Victoria Beckham Autumn Winter 2013 (source: style.com)

In a few days I am attending a conference for work and I have been invited to speak up for a video interview. Nothing really fancy to be honest but I got really confused with the clothing guidelines: no white, no red, no black, no stripes, no busy patterns, no hot or bright color tones. Mmmm. Exactly. And because for some reason (aka Victoria Beckham) I think I should be wearing a dress all I have to do is find one fitting the (strict) guidelines...
From top left: cobalt blue dress (philosophy by alberta ferretti), navy blue and white dress (whistles), crepe blue dress (vivienne westwood anglomania), navy turtleneck dress (alice + olivia), two-tone dress (theory)
Which one do you think I should get ?
Any other suggestions would be welcomed !
xx Marta