I don't find it off-putting (perhaps I'm just accustomed to the CSS styling used for beta sites).

I find the block quotes OK (functional):

- Readable (dark text on pale background)
- Distinct (easy to see the difference between quote and non-quote)

Historically when people ask about styling their beta site, SE have said they'll give a site custom styling when it graduates from beta.

I've up-voted your question/suggestion on meta.SE though: because why not.

The first thing (and almost the only difference) I see when I looked at the [example style](http://www.buddhismwithoutboundaries.com/showthread.php?5476-Is-There-a-Criterion) you posted is that the non-content (extreme left and right) margin is yellow. Content remains black-on-white, with yellow (or do you see that more as a distinctly orange shade of yellow?) for the block quote.

It has a yellow instead of blueish top banner though, too, so "warmer colours" overall (as you said) instead of "the yellow+blue look".

If you look at a page of a graduated SE site [like this one](http://bicycles.stackexchange.com/q/7708/1097), the margin is coloured (see a slightly grenish blue) and the content background is still the simple near-white. Maybe (I'm not a style designer) a whiteish background is good because it accepts various-coloured text (including colours for links and visited links). And the block quote is yellow. 

Still, some SE sites have non-white content, for example [this one](http://english.stackexchange.com/q/241777/9548), so that's not impossible either.