change color caption title on slider

Rikards way is the best – give a custom-class to your slider and let it be part of the selector to the heading you like to change
the custom-class will be on the slider itself (

.custom-class .avia-caption-title {
    color: red;
}

(maybe an !important is neccessary)

btw: there is no class : avia-caption on the tree there is : slideshow_caption

Edit: sorry on easy slider there is avia-caption class !

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next if you like to influence it in dependency to the slide you had to insert slide class ( slide-1, slide-2 etc.)

.custom-class .slide-1 .avia-caption-title {
    color: red;
}

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BUT: there is the way in the slider ALB Element itself to change the font-color:
On Styling Tab you got:

Edit: sorry on easy slider there is this option missing – only for full-screen or full-width slider

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offtopic:
well this is not the right way.
There are attribute selctors that could be used. – You find a good list f.e. here https://developer.mozilla.org/en-US/docs/Web/CSS/Attribute_selectors
but even those selectors are outside the curly brackets f.e.:

.anotherelement img[src*="yourpic"] {
your css code here …
}

that littel asterisk means : contains at least one occurrence of value (yourpic) within the string
the list is big see link above ( *, $, ^, ~, |, etc. pp )