[support] Modify calendar css

I'm hoping someone can advise me on this please.

The Calendar in Drupal 7 has grey print on yellow background and is very difficult to see. I found that it could be modified in the <div class="calendar monthview"> in the calendar css but when calendar module is updated the change is lost.

I'm thinking of creating a my.css file and putting modified css lines into that file but I'm uncertain of the details. I think it needs to be included the theme.info file in the css list... should my.css go at the top of the list or at the bottom sot hat it over rides the module css.

Also in which folder should css overrides be placed so they co not get over ridden by updates. thanks in advance Roger