Something else you may like to consider is the use of the red soil as mentioned in Chris's post.
The use of red materials in prehistoric graves is well known and extends back into the paleaolithic.
I know of two North Yorks burials were red was deliberately placed in a funery monument.
One was a burial discovered in a rock fissure (? windypit), just north of Pickering where the body was embeded in a layer of stiff red clay. The second was a grave beneath a barrow at Scamridge where the skeleton was laid upon a bed of deliberately chosen red gravel.
Many believe that the blood red colour may be a symbol of life itself.