Your videos and images never leave this device: they are opened and read in this browser only, never uploaded, and there is no account. Only the colors you save (with the file name and frame time) are kept here, so save a backup file now and then.
Color picker for video frames
Open a video, stop on the exact frame and pick a pixel with the loupe. Copy the value in five formats, collect colors and export them as a palette.
Values are what this browser decoded, in sRGB. HDR, wide-gamut (P3), 10-bit or log footage is tone-mapped by the browser, so values can differ from your editor or the original file, and lossy video shifts colors slightly near edges.