Towards the end of the episode, it showed little amy in the garden and you could here the tardis materialising as if he was going to change future history and go back and visit her when originally he didnt go back.
Also the other bit was when amy stuck the doctor in the car with his tie, he said trust me for 20 minutes, showed her an apple, and then all blue started appearing on the screen?
What were the 2 above bits about, any ideas please?

I thought he was going back etc, the blue hue was meant to signify the growing trust and friendship between the 2.

I think the little Amy in the garden was just the big Amy in the present dreaming about being the little Amy in the garden when the Tardis materialised.

Didn't the adult Amy then wake up ? I assumed she was dreaming of herself as a child waiting for the Doctor to return, much like she had spent the last 2 years!

On first viewing I thought that he'd gone back as promised to make sure Amy did not grow up thinking someone else had let her down by leaving. I thought it was really funny that he missed adult Amy by two years, meaning she will still have that anger about him letting her down.

My girfriend then pointed out it was a dream in the present day with Amy probably dreaming all the time that the Doctor came back.

I'd agree with the other posters that little AMy hearing the engines was just their sound in the present day intruding into the adult Amy's dream, but the blue - well I have no ideas about cameras and optics but was it unintended lens flare or somesuch? Maybe it was intended but if so it seems a strange decision to add a special effect that rather than being special just looks like an unwanted effect.

The blue was just meant to be a bit of mood lighting, a little touch to highlight the moment.

But you can't really do 'little touches' in Who, cos for some fans, everything has to mean something. It's like all that fuss over Donna's ring a coupla years ago.

There was lens flare throughout the episode. I think maybe to give it this fairy tale feeling they were talking about on confidential.
On first sight it did seem to come out of nowhere on that particular shot (very J.J. Abrams), but on later viewing I noticed they used a spot light from the left (which you can see lighting up Amy's hair) which caused the lens flare.

Does that mean that S7 new era will begin with DT coming out of the shower

I concur with previous posts:

The blue light is nothing more than a camera flare. If you watch DWC they explained they filmed it slower to give the moment impact, as a result they got quite a spiritual moment.

The young Amy in the back garden at the end is part of grown up Amy's dream. The Tardis noise appears in her dream as it is happening in reality and wakes her up.

The blue light was meant to signify the fairytale affect. The whole story was a fairytale between amy and the doctor therefore the blue light showed that and when the tardis leaves for the second time Amy closes her eyes and dreams about the time when the doctor left her before hoping that he will come back and what he said all those years about trusting him, then she wants to believe that and trust him and she wants him to prove that by coming back as at the beginning she said people say that and she knows he isn't just people. The tardis interrupts her dream when it returns and she knows that dreaming her time before brought him back.

1. As others have written, the adult Amy was dreaming of being the child Amelia waiting for the Doctor. The sleeping Amy hears the TARDIS and wakes up from her dream;

2. The apple is proof that the Doctor is the same man the child Amelia saw and gave an apple. The apple had been carved with a face (something her mother did). Amy was grappling with whether or not to trust the Doctor and the apple was his way of proving to her that he was the man she remembered and that she needed to trust him "now" as she had as a child.