The icon for inside the Bearsampp system tray, left menu, is in the bar.dat file in the root folder of Bearsampp.
Replacing the image in the icon tray takes a few steps...

1. Create a 32x32 pixel transparent png
2. Go to https://onlinepngtools.com/convert-png-to-bmp and convert that png to a .bmp
   1. Change the background color to match the color in core\classes\tpls\class.tpl.aestan.php 'BarGradientEnd=$0030BF00' & 'BarGradientStart=$0030BF00'
   
3. Now choose "Save as" and save it as "bar.dat" into the root of Bearsampp