Just thought I'd pass this on. I won't take any credit for this as I found it in the coding forums but it's quite cool to look at.
If you have the HUD, press and hold the HUD switch (down below your light swtiches) for around 10 seconds. you'll then get some diag screen pop up, everytime you press the HUD button, the screen changes. Didn't count but there's something like 15 different screens varying from RGB colours and a grid to sample screens , some of which are in Japanese.
And also found this , not for the F10 but the E70 but explains the HUD in detail as well and I assume it's pretty much the same for the F10.