Wireshark tcptrace colors ack numbers from reverse packets highest number (most recent) SACK block subsequent SACK blocks forward data segments on tcptrace graph https://github.com/wireshark/wireshark/blob/3a514caaf1e3b36eb284c3a566d489aba6df5392/ui/qt/tcp_stream_dialog.cpp#L239 https://github.com/wireshark/wireshark/blob/master/ui/qt/utils/tango_colors.h