WordPress Twenty Thirteen Theme
My initial impression was that it was too bold to be useful on a large scale. But I think that bold is good, because it highlights the rarely used post formats more than any theme I have seen – certainly moreso than the three other default “Twenty-something” themes that have come before it. Even if we scale it back a bit via child themes, we will have no choice but to call out the different post formats (and maybe even use them…)!
And just in case you don’t like orange, Otto has created a blue version.