Slideshow Classic: a colour per line of text
Give the eyebrow, heading and subheading their own colours, or leave them empty and keep one colour for all three.
Slideshow Classic used to paint the eyebrow, heading and subheading in a single Text colour. Now each one can have its own.
Open Colors and you will find three new pickers under Text: Eyebrow color, Heading color and Subheading color. Leave any of them empty and that line keeps following the Text colour exactly as before, so nothing changes on the slideshows you have already built until you decide to change it.
A small detail worth knowing: the eyebrow and subheading are normally softened slightly so the heading leads. The moment you choose a colour for one of them, that softening lifts and you get the exact colour you picked. A softened colour blends with the photo underneath, so it is never quite the colour on the swatch.
Also fixed: on some themes the slideshow text was picking up the theme's own heading and paragraph colours instead of the Text colour you had set. That showed up most often as dark text sitting on a dark photo. The slideshow now states its colours outright, so your setting wins.