Remove the @color parameter so the striped color does not match the background-color. It might be a good idea to provide a second parameter to the progress-bar-varient() mixin to control the striped color. Example below.
```
.progress-bar-varient(@background-color; @striped-color) {
    background-color: @background-color;
    .progress-striped & {
        #gradient > .striped(@striped-color);
    }
}
```