[support] Modify calendar css

[Roger]

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