Deep indigo blue can be a very formal color. It gives off an old world feel and is very common in Moroccan-inspired decor. Use light accessories in gold or silver and lots of mirrors to create a great balance.
Is turquoise a blue or a green color? Well, the answer is that it's both. But what's really important is that turquoise has been making a comeback in recent years and is the #2 color in interior decorating this year (right after smoky green). Turquoise has a very calming effect and it's a great color for beach house design. For accents, use colors that you'd find on the beach - sand, dirty white, coral, grassy green and sunshine yellow.
And speaking of comebacks...
...Years ago, a painted accent wall was all the rage and designers were debating what was considered an accent wall and what was not. Nowadays, it's out with the paint brush and in with the wallpaper glue. Today's homeowners pick the wall that has the most architectural or artistic interest and cover it in fancy damask print wallpaper.