python-gallery/usr/themes/default/buttons/btn.scss

@mixin button($color) {
    border-color: rgba($color, 0.3);
    background-color: rgba($color, 0);
    color: $color;

    &:hover {
        background-color: rgba($color, 0.2);
    }
    &:active {
        border-color: rgba($color, 1);
        background-color: rgba($color, 0.5);
        color: $color;
    }
}

.btn {    
    padding: 0.5rem 1rem;
    border-radius: 0.25rem;

    border: 1px solid rgba($white100, 0.3);
    background-color: rgba($white100, 0);
    color: $white100;

    transition: background-color 0.3s ease-in-out, border-color 0.3s ease-in-out, color 0.3s ease-in-out;

    &:hover {
        background-color: rgba($white100, 0.2);
    }
    &:active {
        border-color: rgba($white100, 1);
        background-color: rgba($white100, 0.5);
        color: $white100;
    }

    &.red {
        @include button($red);
    }
    &.orange {
        @include button($orange);
    }
    &.yellow {
        @include button($yellow);
    }
    &.green {
        @include button($green);
    }
    &.blue {
        @include button($blue);
    }
    &.purple {
        @include button($purple);
    }
}