I was just marveling at my 'Bloodgood,' which should have absolutely crimson leaves.
It's a weird not red-not green color, too.

I have some with new growth, because the heat killed their existing leaves, which are coming out in their true-to-form colors.

I'm hoping things make it through this drought. 3 rains in 18 weeks. arrrghhhh!

I think with more water, next year, they'll be red again. When we care? They do weird thing.

Christine

Hi Christine, Since I'm so new at this I don't know if this makes sense. A lot of my plants are in containers. My Japanese maple only did well in total shade. It's quite happy only in one specific spot. And the leaves have been crimson for awhile. I was lucky.

I was going to post this same thing I've got a full grown what I believe is a 'Bloodgood' Japanese Maple that has been red every year except this year. We had a lot MORE rain than usual this year so I assumed that was the cause of the green leaves but it hasn't rained in a while now and they never turned red. Perhaps the nutrients got washed out of the soil? It looks like we are ALL still in question on the why here so... RESEARCH TIME!
This is the best information that I found:

Japanese red Maple leaves turn from red to green when the intensity of light is decreased.
Most if not all varieties of red leaf plants lose the red color if the leaves are in a shaded area. Our trees are grown close together to conserve water and help keep plants standing.This causes the new upper most leaves to become very red and the leaves that are shaded by other leaves to become green. Once these trees are given more space the red color comes back." (1)

Here's another interesting point:
"Trees grown from seed lose their red leaf color in summer, which may be disappointing to the homeowner. " (2)

My tree is in a fairly shady side of the house and is full grown now so there will be no moving it for me... I do think that all of the overcast rainy weather did send it into the green state that it never got out of though.

Hope this helped some of you!

Here is a link that might be useful: Sooner Plant Farm

I just found out at another web site that most Japanese maples sold at nurseries are red variants grafted onto green variant root stock. Apparently greenies are easier to propagate.

I bought a red tree last year, but the top froze and died (surprise cold snap)...I was thrilled to see a shoot coming up from the base, and it's grown in nicely, BUT it looks like I got a green variant stock and the beautiful focal point I expected to see framed by green hostas and grasses is now almost invisible because it blends in with everything else....grrrrrrr!!!