ffmpeg overlay png on video has color issue

Im trying a simple overlay command to put a logo on a black video, but find the color a little different in output, the original RGB value of green part of the logo is (0,220,90), but changed to (0,191,88) in output. Looks like the color gets mixed with the black background, any ideas?

original logo rgb:

rgb after logo overlayed on video:

the command to overlay:

ffmpeg -i video.mp4 -i logo.png -filter_complex "[1:v]format=rgba
展开收缩
,[0:v]
展开收缩
overlay=240:1275:format=auto" output.mp4

the logo and video:

▶ ffmpeg -i logo.png               
ffmpeg version 4.4-static https://johnvansickle.com/ffmpeg/  Copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 8 (Debian 8.3.0-6)
  configuration: --enable-gpl --enable-version3 --enable-static --disable-debug --disable-ffplay --disable-indev=sndio --disable-outdev=sndio --cc=gcc --enable-fontconfig --enable-frei0r --enable-gnutls --enable-gmp --enable-libgme --enable-gray --enable-libaom --enable-libfribidi --enable-libass --enable-libvmaf --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librubberband --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libvorbis --enable-libopus --enable-libtheora --enable-libvidstab --enable-libvo-amrwbenc --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libdav1d --enable-libxvid --enable-libzvbi --enable-libzimg
  libavutil      56. 70.100 / 56. 70.100
  libavcodec     58.134.100 / 58.134.100
  libavformat    58. 76.100 / 58. 76.100
  libavdevice    58. 13.100 / 58. 13.100
  libavfilter     7.110.100 /  7.110.100
  libswscale      5.  9.100 /  5.  9.100
  libswresample   3.  9.100 /  3.  9.100
  libpostproc    55.  9.100 / 55.  9.100                                                                                                                                            
Input #0, png_pipe, from 'logo.png':
  Duration: N/A, bitrate: N/A
  Stream #0:0: Video: png, rgba(pc), 601x81 [SAR 2834:2834 DAR 601:81], 25 fps, 25 tbr, 25 tbn, 25 tbc

▶ ffmpeg -i video.mp4                                                                                                   
ffmpeg version 4.4-static https://johnvansickle.com/ffmpeg/  Copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 8 (Debian 8.3.0-6)
  configuration: --enable-gpl --enable-version3 --enable-static --disable-debug --disable-ffplay --disable-indev=sndio --disable-outdev=sndio --cc=gcc --enable-fontconfig --enable-frei0r --enable-gnutls --enable-gmp --enable-libgme --enable-gray --enable-libaom --enable-libfribidi --enable-libass --enable-libvmaf --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librubberband --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libvorbis --enable-libopus --enable-libtheora --enable-libvidstab --enable-libvo-amrwbenc --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libdav1d --enable-libxvid --enable-libzvbi --enable-libzimg
  libavutil      56. 70.100 / 56. 70.100
  libavcodec     58.134.100 / 58.134.100
  libavformat    58. 76.100 / 58. 76.100
  libavdevice    58. 13.100 / 58. 13.100
  libavfilter     7.110.100 /  7.110.100
  libswscale      5.  9.100 /  5.  9.100
  libswresample   3.  9.100 /  3.  9.100
  libpostproc    55.  9.100 / 55.  9.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'video.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.76.100
  Duration: 00:00:02.00, start: 0.000000, bitrate: 24 kb/s
  Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1080x1920, 18 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
    Metadata:
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]

The issue is related to color formats.

FFmpeg default YUV color standard is BT.601 - FFmpeg converts from RGB to YUV using BT.601 color conversion formula.
FFmpeg uses BT.601 but doesn't mark the H.264 stream as BT.601 (FFmpeg default is not setting the color format metadata of the video stream).

As far as I know, the video player assumes the color standard is BT.709, because the video is HD (more than 720 video lines), and the recommended standard for HD video is BT.709 (it may be different in different players).
The video player converts from YUV to RGB using BT.709 color conversion formula, and we are getting the color differences.

I recommend you to convert the video to BT.709, and mark the video as BT.709:

• Convert the video to BT.709 using scale filter:
  scale=out_color_matrix=bt709:out_range=tv

• Mark the video as BT.709 "TV range" (Limited range) using bsf filter:
  -bsf:v h264_metadata=video_full_range_flag=0:colour_primaries=1:transfer_characteristics=1:matrix_coefficients=1

It's also recommended to specify libx264 encoder, and set the crf and pix_fmt arguments:

ffmpeg -y -i video.mp4 -i logo.png -filter_complex "[0:v][1:v]overlay=240:1275:format=rgb,scale=out_color_matrix=bt709:out_range=tv" -vcodec libx264 -crf 17 -pix_fmt yuv420p -bsf:v h264_metadata=video_full_range_flag=0:colour_primaries=1:transfer_characteristics=1:matrix_coefficients=1 output.mp4

There are still minor inaccuracies due color conversion rounding.
For preventing any rounding error, we may use libx264rgb encoder, but the video my not be very portable.

logo.png:

output.mp4 played with MPC-HC media player:

output.mp4 played with VLC media player:

We may check the color standard (metadata) using MediaInfo tool:

Color range                              : Limited
Color primaries                          : BT.709
Transfer characteristics                 : BT.709
Matrix coefficients                      : BT.709