With deep red background, however, there was no color printing technology, so finally are black and white photos.

虽然采用深红色背景拍摄，然而当时并没有彩印技术，故拍出的都是黑白照片。

youdao

Three (3) identical photos, colour or black and white taken against a plain white or light coloured background within the last 6 months.

申请人需递交三张相同的在最近六个月内拍摄的彩色或黑白照片，背景为纯白色或浅色。

youdao

Single photos will now be displayed full screen -- the size options and white background have been nixed for the extra real estate.

ENGADGET