I have just got a Orange SPV M600. I know it's possible to change font size and get custom today screens. But when I use the Phone. The phone screen with soft keypad is an awful colour. The text is black on a dirty gray background. Is there anything I can do to change to colours in this application ?

I too hate the standard dialer skin as you can not read it even in nornal daylight. After surching and trying various skin changers I came accross this page: http://www.htcwizardweb.net/node/647#comment-1054
This allows you to remove the ugly Orange skin and resorts back to Microsoft's blue skin, but so far I an still unable to install different skins (but I finfd the blue one a lot better).
The only downside is that it gets rid of the drop down list you get when you enter phone numbers.
You also need Tool Commander, have not got URL for this but just Google for it.
Hope this has been any help.