[Martin Noel]

I was able to change all my titles on my timeline from black to white once. I added a quick color correction effect to one of the title text, I played with the exposure to get the text from black to white, saved the effect as preset. Then luckily all my titles card were on the top three tracks on my timeline so I selected the whole three tracks (drag mouse from beginning to end). Then I dropped my preset effect to my selected tracks and then all my titles in the timeline were changed from black to white.

You can do that with any effect that you want ( I played with the color wheel and hue to change the color too)