How does col.regions work in spplot?

Dear Ken,

if I understand correctly, you want to create a plot without highlight 
borders. This can be achieved by setting col="transparent".
using your example, try:
spplot(nc, zcol = "rand_data", col.regions = heat.colors(100), 
col="transparent", colorkey = T)

I don't know how to set the colours of the borders individually, but I 
think the solution above produces a plot looking like you wanted it.

Cheers,
Mathias

Mathias Seibert

Sektion 5.4 Hydrologie
Tel.: +49 331 288 1513
Fax: +49 331 288 1570
Email: mathias.seibert at gfz-potsdam.de
___________________________________
Helmholtz-Zentrum Potsdam
Deutsches GeoForschungsZentrum GFZ
(GFZ German Research Centre for Geoscience)
Stiftung des ?ff. Rechts Land Brandenburg
Telegrafenberg, 14473 Potsdam