Hi John, welcome to silver-collector.com
The yellow colour you see on the blades of the knives could be one of two things. Either they are very very tarnished and you haven’t cleaned them in some time… Or, (which is much more likely) the blades have been gold washed, or gilt. This was done to protect the blades from attack by salt etc, and also to stop you from polishing them and then poisoning yourself with silver polish.
As for value I would estimate them at around £15 each, or £70 for the set.
Hope this helps, and thanks for joining us on the forum.