Colours are different in Internet Explorer

Hi,
I’m hoping someone can help.
I have designed a website which looks lovely in all browsers except Internet explorer where it is not displaying the colours I have set, for example, in my home page the first section background should be green with white writing, IE is showing it as a white background with blue writing. Having looked through every page, it looks like IE isn’t showing my green colour anywhere on my website. I have used Astra theme in case this is relevant. Does anyone know what the problem is?
Many thanks

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