Retrospring/app/assets/stylesheets/overrides/_buttons.scss

@each $color in $colorNames {
  .btn-#{$color} {
    background-color: var(--#{$color});
    border-color: var(--#{$color});

    &:hover {
      background: linear-gradient(
        to top,
        rgba(0, 0, 0, 0.10),
        rgba(0, 0, 0, 0.10)
      ) var(--#{$color});
    }
  }
}