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/* change bootstrap 4 tooltip colors, including the arrow ! */
.tooltip-inner {
    background-color: #555;
}

/* tooltip top arrow */
.tooltip.bs-tether-element-attached-bottom .tooltip-inner::before, .tooltip.tooltip-top .tooltip-inner::before {
    border-top-color: #555;
}
/* tooltip bottom arrow */
.tooltip.bs-tether-element-attached-top .tooltip-inner::before, .tooltip.tooltip-bottom .tooltip-inner::before{
    border-bottom-color: #555;
}
/* tooltip left arrow */
.tooltip.bs-tether-element-attached-right .tooltip-inner::before, .tooltip.tooltip-left .tooltip-inner::before{
     border-left-color: #555;
}
/* tooltip right arrow */
.tooltip.bs-tether-element-attached-left .tooltip-inner::before, .tooltip.tooltip-right .tooltip-inner::before{
     border-right-color: #555;
}