A text layer and matte layer show as a black background, I want to change the black to another colour.

I found a training video that uses a blue Matte v1 a video V2, and a text layer v3. The video when running shows a black background to the screen, the text appears as the blue Matte colour.Further in the timeline the video hen appears through the text as an effect.

My sticking point is the text is Matte Blue, then transparent to show the video behind. I want the background to be a colour of my choice, NOT black. Any suggestions?

The end effect is this