Product theme: some styling questions

1. I have been playing around with my colour scheme and have found two things that won't change colour when I put a colour in the custom styling:

A. slideshow pagination link active background colour
When I change the link colour it changes, but the background stays a light grey. I have it set to black and you can see it is grey. http://ukmarketingnetwork.com/

B. buddypress navigation hover text colour
I have it set to a pinky colour yet when you hover over the text it is black.

Another odd thing here is that whatever colour I put into slideshow pagination link colour it changes slideshow pagination border colour to the same colour - is this supposed to happen? I can't change the border colour it just reverts to the link colour.

2. In IE8 is when you click on the navigation arrows on the side of the slide show small dotted black line appear above and below the arrow - not visable in google Chrome. Any idea about this?

3. The last question: I want to change some text sizes and I have never worked with child themes before and would like to know which CSS I need to change and where it is. I assume this is the only way to change sizes as the style option only allows colour change.