NZFF

It is not only in this area. I have the water in the foreground wich is much brighter as the smal sea in the background. Here is the water fare more dark. Sometimes it is in the middle of the sea. I have not found such things in europe in the last time...

I have the complete package of Godzone-Szeneries, VLC NZ and REX 2 in use. First thing I do is to change the theme in REX 2 and if I can´t found a theme blending with the scenerys it seems, I must create one.

Hope, here I can find other virtual pilots with more experience and ideas, maybe a solution that exist but i don´t know...

Lake Tekapo photo scenery includes a photo of the lake, rather than default water textures. In FSX the photo is blended with REX textures, and this doesn't always give the result you would expect.
However the colour in your screenshot is accurate -- Lake Tekapo is glacier-fed, and the blue colour is caused by suspended particles in the water, whereas Lake Alexandrina -- the little lake in your screenshot -- is not fed by the glacier, so it is a completely different colour. Getting these to work together with REX would be a beyond the capabilities of FSX, I think.

Here's the lakes in Google Maps, you can see the actual colour of the two lakes quite well.

Those two lakes really are different colours in real life. Lake Georgina in the distance has almost clear water and is a good fishing lake, whereas Lake Tekapo is a teal blue colour due the fine suspended particles in the water (as explained above)

Check out my video flying from CHCH to Queenstown, even in low morning light the difference is still quite obvious. I've named the lakes as we fly by them
http://www.youtube.com/watch?v=Z4KtvIze9M0