advance: my english ist also not so good.
Now back to your problem: you can easily change the colors and more other things. You have to modify the file "style.css". The topic is a little bit complex and would take too much time. I give you the following tip: go to youtube and search for "wordpress", "style.css". You will find so much videos, with a very goog explanation. It´s easy to learn.
Also, I recommend you the Firefox browser with the Firebug addon. By this you can check every website without destroying something (-> youtube).
To the slider: go in the dashboard to "Design - Options - featured Slider - featured post/page slider option". There are the Settings.
And: HERE you find more explanations.
I hope I could help you.
PS: Almost forgot: when you have modified the style.css - create a child theme (again search by youtube!). Otherwise, your changes to the theme will be lost.