I got the following warnings in console when running your app that uses cocos2d-x 3.0
convert: iCCP: known incorrect sRGB profile 'flash.png' @ warning/png.c/MagickPNGWarningHandler/1830.

If you get similar warnings, try running the following bash command
find . -type f -name "*.png" -exec convert {} -strip {} \;

This will use ImageMagick to strip and fix all png files (usually Photoshop and some other editors create bad iCCP chunks)