Ideally, scores are read out using 'to'. For example, 'team blue' has a score of 10 and 'team red' has a score of 20 :
the score is 10 to 20 to team red.
or if you want to specify the team names along with their scores, you could say something like :
team red leads team blue by a score 10 to 20.
As far as 'is' and 'are' are concerned, each game has a single score. So it is generally referred to with 'is'. eg: "The score is 15-to-love".
Please note that in some cases, take football (soccer) for example, consider a game in which Brazil lost to Germany with a score 7-1. Now, the score (goals) can be said to a second person using the following format :
Brazil lost to Germany seven-one.
There are a few ways to mention the score, but a lot of them are sport-specific. Generally, you could say 'to'.