No, you do not need to paint with acrylics, although acrylics are suggested.
We have quite a few artists who complete Bold Color Bootcamp in other mediums, mostly oils and watercolors. We also do have a new series in oil painting which focused on Landscapes.
Although Charla teaches about working with acrylics, much of the Bold Color technique can help you loosen up and work with bold, abstract color in a new way regardless of medium.
Please note, some aspects (such as layering) do not translate as well, but there are many applicable topics including workflow, drawing a face, color mixing and troubleshooting that will benefit artists who are not painting with acrylic paints.