Here's a little background for you:
http://espee.railfan.net/passenger-paint.html
Of course while the Daylight colors were popular the SP was also running the Lark in a gray scheme similar to Pullman pool colors.
The silver and red was probably an attempt to get the cars to mix better with the Budd and Stainless-sheathed P-S cars:
SP_Houston-69 by Edmund, on Flickr
There were still some Daylight-painted cars still around in 1969:
SP tripple-unit dining car-dorm kitchen-coffee shop cars 10262, 63, 64 in storage at Houston, TX on June 5, 1969 by Marty Bernard, on Flickr
Good Luck, Ed
Hi. Does anyone know approximatley when SP changed their "Daylight" red and yellow/orange color scheme on passenger trains to the standard Pullman built cars with all silver and a red letterboard? Thanks for checking.
JRP