If I would design the safety cards, I would make most of the cover navy blue with a large red Widget. It would include Delta's new logo, and all other text would use Delta's new font found in many of their new advertisements.

For the colored tab, I would actually use a a vertical gradient of two different shades of the same color. Also, I don't see the point in having different safety cards for the domestic 767-300s and 767-300ERs (except for the ex-Gulf Air aircraft), as their exit layouts are the same.

Here are my suggestions for the new ones:
MD-88 - Brown

MD-90 - Teal - V3

737-800 - Yellow - v3

757 - Violet - V4

757 ex-TWA - Orange - V1

767-300/300ER - Green - V7 (V3 + V4 = V7)

767-300ER ex-Gulf Air - Blue - V5

767-400ER - Pink - V4

777 - Red - V3