Change background colour of link buttons throughout site

Hi my website is https://www.totsoffun.org.uk I would like some CSS to change background colour of the link buttons throughout site including on our shop page. I have played around with some additional CSS and managed to find some that worked with some of the the link texts but not all. Id like to change the red button backgrounds to a teal colour and preferably have white text. Can I do this with out altering other links that might not have a coloured background button? Your help would be most appreciated. Lottie