Worked for me:
Stable V4.2
QGCApplication.cc
lines 264-268, specifically in line 267:
ifdef DAILY_BUILD
applicationName = QStringLiteral("%1 Daily").arg(QGC_APPLICATION_NAME);
#else
applicationName = QGC_APPLICATION_NAME;
remove the word Daily here.
About the colors:
open QGCPalette.cc
and go to lines 88-90:
DECLARE_QGC_NONTHEMED_COLOR(brandingPurple, "#1E3582", "#1E3582")
DECLARE_QGC_NONTHEMED_COLOR(brandingBlue, "#878686", "#878686")
DECLARE_QGC_NONTHEMED_COLOR(toolStripFGColor, "#707070", "#ffffff")
change the HEX values here to your colors, for example the top color is the color of the left side of the top title-bar.