What's the logic behind textbackground light/Dark

[Edward]

Hi,
This new 12 color option in colorscheme in PP2007 seems to me confusing .
When I customize those colors Accent 1 to Accent 6 are straight forward (
although in VBA still we need to know that accent 1 is our old fill and still
uses fill )but first four text/background light/Dark are very confusing .
when I change them it seems they only apply the slide 1 and also I can’t
understand them well ( especially because they have the same name and I
couldn’t find any documentation in MSDN ) . Can someone explain what are
these 4 colors and how they exactly work ?

 

[Echo S]

These are designed to ensure that your text is always visible on a
background.

Basically, if you choose a light background option and you have dark text,
then when you switch to a dark background, PPT changes automatically to
light text.

You can see this by going to the design tab and playing with the Background
Styles palette -- there are 12 options there, based on the light/dark
combinations. (Try the Urban theme -- it's generally a good example of
this.) You'll see the text change automatically as you pick a different
background style.