It seems that changing the value to something different than the default of a Linear Color Struct variable, results in the value being changed when upgrading the project to a new engine version. This is not exclusive to the DrawDebugCamera node as it seems to happen with any node that has a Linear Color Struct input node.
The value of CameraColorA reverts back to the default value of 1.0
The values are maintained when upgrading to a newer engine version
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-136524 in the post.