A little experimentation with the track values you can change in the settings dialog will yield values in their registry variables that can then be copied to the clip background variables.  For instance, ffffff (hex) will produce white backgrounds.

Come on... who's not impressed with how nice my DAW looks?

Acura, a car company made this statement once: We make hard and solid decisions to find the best middle ground with all users and choose colors that, not only will give you the best looking cards on the road, but also to minimize the color options we have to produce."

 
White, Gray, Black, Beige, White, Black, Gray... wait...

alewgro
Come on... who's not impressed with how nice my DAW looks?

I've always enjoyed pastel-shaded clip backgrounds for audio clips, myself, too.

I don't like the pastels myself - but that's why we want it "customisable" ;-)

alewgro
Come on... who's not impressed with how nice my DAW looks?

 
That sorta reminds me of Smarties...   
 
http://en.wikipedia.org/wiki/Smarties_Candy_Company
 

stevec

alewgro
Come on... who's not impressed with how nice my DAW looks?

 
That sorta reminds me of Smarties...   
 
http://en.wikipedia.org/wiki/Smarties_Candy_Company
 

Sorta reminds ME of OTHER DAWS!  ;)

I'm pretty happy with the X3/Platinum color options.
However I do wish there was a way to alter the preset color swatches on the "Pick Color" palette. Here's my current setup, which I've grown to like a lot:
 

 
Of course, a real project doesn't look quite so rainbow-esque.
The trick is to find the right color value that looks good as a waveform (pure) and console/strip shade (grey tint).
 
It also has to work with selected/muted/frozen options in a sensible way. 
 
I'm not saying we should stop asking for clip background colorization options; I'm just saying, if you were new to SONAR and didn't have any preconceived ideas about how the track view would look, I think you'd find this pretty darn purty.
 
Color Customization
===================
name    R   G   B
------- --- --- ---
RED     166  68  51
BROWN   194 114  75
YELLOW  204 192  45
MOSS    138 175  50
GREEN    66 157  68
CYAN     82 173 155
BLUE     55 146 200
INDIGO   91 114 219
PURPLE  142  96 230
VIOLET  193 123 193

Yup, looks pretty good here.   You have a point about new(er) users that don't have pre-defined color setups; what's currently offered would likely work well.  
 
If you add the preset color swatch as a feature request I'd star it - I could definitely use something like that.
 

For newbies who do not go back to 8.5.3, maybe they do not know what they are missing.  But that is a poor excuse not to have a great feature that was there in the past -- i.e.  to be able to set a track color and have them stay that way for new clips that are recorded.  I spend a lot of time recording new clips and having to change the colors to match the rest of the track, manually.   Still an AWESOME PROGRAM.  But please address this or tell us it will not be addressed.