VMS Help Sys Parameters, PFN_COLOR_COUNT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 (Alpha only) PFN_COLOR_COUNT specifies the number of buckets
 (colors) into which all members of the zeroed page list and all
 unencumbered members of the free page list are sorted. OpenVMS Alpha
 systems might derive a preferred page color from a request to map
 a given virtual page and attempt to map that virtual page to a PFN
 of matching "color." This results in less variance in which cache
 blocks are used when accessing that page. This might or might not
 improve performance, depending on the application.
    This special parameter is used by Compaq and is subject to
    change. Do not change this parameter unless Compaq recommends
    that you do so. If you increase this parameter, you must also
    increase the ZERO_LIST_HI system parameter.