Often setting a button/anchor text color is not effective because the theme likely targets anchor tags directly such as:

.some-class a {
  color: #000000;
} 

And Elementor's color control within the text property results in:

.elementor-uniqueue-class .elementor-button {
  color: #ffffff;
}

But this won't override the color because the selector hierarchy is insufficient as the anchor element is higher in specificity than the .elementor-button class. However, if you simple add the selector, problem solved!

.elementor-uniqueue-class a.elementor-button {
  color: #ffffff;
}