Q.cutting red tip yucca
I have a red tip yucca that is ten years old. It has 40% dead vines. If I cut it to six inches in height, will the green vines grow back?
By vines, do you mean the flowering stems? You are going to want to cut the flowering stems down to the base once they are dry and brittle. Same goes for any dead leaves (foliage) - cut those down to the base as well. And yes, everything will grow back. :)
For more information about pruning yucca plants, please visit the following link:
https://www.gardeningknowhow.com/ornamental/foliage/yucca/yucca-plants-care-and-pruning-tips-for-pruning-a-yucca.htm