Readability is actually part of the reason those were chosen
![Wink ;) ;)](/styles/default/xenforo/vbSmilies/Normal/wink.gif)
We've got several lovely looking sets that unfortunately are a little hard to read in poor lighting due to the colours used lacking contrast*, and as much as I love some of the GW dice, they can be hard to read if you don't know them (IIRC a couple of their themed dice have icons/symbols on both the 1 and 6 facing).
Younger brother is having the top left for his Necrons, and Top Right for his Nurgle/Dark Angels, whilst top middle is pretty close to the colour scheme I use for my Tau (shadow grey+ fortress grey with fiery orange sept markings)
*Something we've discovered when in a friends garage, fancy swirly dice that look great in good light are often harder to read than his millions of plain ones.