White heavy tape about 2" wide (50mm) was wrapped around posts, sticks and trees bout 12" above the ground to mark all walk ways, tracks and trenches, at and near the front lines. This was so that troops could see their way around at night time. No lights were permitted as this would attract enemy fire. In the photo below the tape is show in the centre of the photo.
Bright coloured crosses were placed on the southern side of hills so our aircraft could see that it was a friendly position, and not bomb or strafe us. The crosses and colours were changed from time to time so as the enemy could not use a similar method. While I was in Korea they were using bright iridescent red - orange or yellow. In the photo below you can see a cross a fraction to the right of the centre.
Ernie R. Holden.