I'm thinking browbands - is his face more white or more coloured? What 'skewbald' is it? Chestnut, bay or brown based?
No white, it will disappear into his white markings. Depending on how dark he is, you either want bright colours or darker neutrals. I have baby blue, chocolate and cream on my foal, she is solid coloured though. On my (again solid) bay I have navy, gold and cream or purple, white and silver, and both look fabulous. It depends on the horse. Greens and blues look fabulous on chestnuts and bays, traditional red/white/blue looks awesome on most colours (but not too much white in your case). For saddle blanket/bandages/halter you would want to pick a colour from the browband that contrasts both the markings and the base colour.
Is your cob a true tricolour or a bay and white pinto? On a bay and white pinto I would strongly suggest shades of blue or shades of green, perhaps with some red in there. Purple would also look lovely.
OK so bay/white then :) Blues and greens would look gorgeous. I personally would recommend blues to really set off the blue eye. If I was making a ribbon browband for this horse, I would go royal blue, navy blue and baby blue, with a touch of silver for bling. Royal or navy for the saddle pad/bandages/halter/whatever, baby blue would fade out a little bit - you would want it and silver to be the 'minimal' colours and royal and navy to be the strong 'theme' colours IMO.
Your horse looks a lot like Sinatra to me, the one in my avatar. When we rode Sinatra in drill team about 3 yrs ago we used dark purples for him. Anything too bright and you're asking for a seizure with a tri color paint!
Its just sooo difficult, I have asked everyone on the yard and everyone says different. I like the blue idea... as he is my fist ridden horse I went a bit wild on the bridle and got him one with Blue diamontes in the browband (have to have a bit of cheap'ness with your 1st) lol.
I'd go royal or navy blue with your boy, ShowStopper. Bays look good in blue. Although, my old gelding was a bright bay touched with gold (if you've ever seen the cover of Marguerite Henry's book "King of the Wind," he had the exact same coloring as the horse on the cover of that book) and we did red and black lumberjack plaid (he was small, but he was mighty!). It was absolutely adorable!