I managed to change the checkbox color by changing this rule.
But I wonder is there a better way than adding this rule to extra.less?
.formRow .iconic>i, .inputGroup .iconic>i, .inputChoices .iconic>i, .block-footer .iconic>i, .dataList-cell .iconic>i, .message-cell--extra .iconic>i, .formRow.dataList-cell--fa>a>i, .inputGroup.dataList-cell--fa>a>i, .inputChoices.dataList-cell--fa>a>i, .block-footer.dataList-cell--fa>a>i, .dataList-cell.dataList-cell--fa>a>i, .message-cell--extra.dataList-cell--fa>a>i, .formRow .iconic svg, .inputGroup .iconic svg, .inputChoices .iconic svg, .block-footer .iconic svg, .dataList-cell .iconic svg, .message-cell--extra .iconic svg, .formRow.dataList-cell--fa>a svg, .inputGroup.dataList-cell--fa>a svg, .inputChoices.dataList-cell--fa>a svg, .block-footer.dataList-cell--fa>a svg, .dataList-cell.dataList-cell--fa>a svg, .message-cell--extra.dataList-cell--fa>a svg {
color: #47a7eb;
fill: currentColor;
}