Thank you for your suggestion, working on it. I'll reply here after successful update

UPD from 11 of April: task complete. Updated version (0.13) submitted. Your local version will be updated in nearest time. You also can update it manually, if you want not to wait :) go to FF menu - addons - extensions - press asterisk and select 'check for updates'). To change colors of translation window - load any website, translate any word to call translation window, then PIN this translation window ( to see future changes ), then press extension icon in taskbar icons group, go to last tab called 'ResWin' and adjust colors. There is HSL color scheme : first bar is SATURATION, 2nd bar is LIGHTNESS and last color bars are HUE of font color and background color respectively. Good luck and have fun! ;)