OK some of your own observations or experiences would be helpful (and BTW your English is just fine )
[li]Do you notice any pattern to it; I mean do all your external subtitles play on the DVDR3480 in green/small font?[/li][li]How about if they are multiplexed in the .avi file… same thing?[/li][li]I presume the subtitles behave normally on other players or the PC…?[/li][/ul]
I’m not suggesting you convert all the files again but it would help us to track down the reasons for any differences. It may be the Philips subtitle rendering that is not right but it would be nice to find a way around that without getting into firmware patching.
I see on a couple of other forums people having the green colour when using external subtitles on the PC video player VLC, but that does have different rendering options.
If you look here there are several subtitle tools that will multiplex or allow editing of the subtitle text. You may like to try some of them…