Adding sweet potatoes and carrots added a nice autumn orange color, and along with the blue potatoes it just added a nice splash of color to the entire meal, not to mention a nice splash of taste.
I chopped up fresh herbs from my garden - rosemary, sage, thyme and marjoram. Mixed in olive oil along with a little finely chopped garlic, salt and pepper. I prepared it all the night before and just put it in the 400°F oven for about 40 minutes until they were crisp on the outside. I did stir it about half way through so it can brown more evenly.
My father used these same herbs to season the turkey he made for our Thanksgiving dinner and it was quite tasty - but you only tasted it if you were lucky enough to get one of the outer slices of turkey meat.
Back to the potatoes... here they are in the pan ready the night before because I knew I wouldn't have time to prep them the day of. Actually, it worked out well because they "marinated" over night and really infused the potatoes with flavor.
The only caution I would give is that all of these potatoes cook at a different rate so the textures varied. The blue potatoes ended up a bit dry and tough - pretty to look at but not the tastiest IMO. The sweet potatoes cook quickly and did not crisp - they were on the soft/mushy side, but I didn't mind and they tasted great.