I was trying to repeat tuto at

https://linuxvideoediting.blogspot.com/2022/01/transparent-text-effect-in-Cinelerra-part1.html?m=1

so I loaded video, created empty new vid track, applied 'titles', 'blur' and 'invert video' to _empty track_, then set track's mode to subtract .... result was color inversion of original video on second vid track (