Colours keep chaning when i try to upload a vector image to instagram

Since you describe the colour change as quite dramatic ("over saturated neon"), I wonder if there is something more than colour management problems going on. I think it might be important if you share before/after screenshots.

Can you post comparison images between what you see exported from Illustrator and what you see on your phone?

As Monika already hinted at, none of this matters if you don't use color management or at the very least educate yourself about how colors are treated differently on different devices, most of which aren't even color managed. The short answer likely is that you are using wrong color settings on your end or have a misconfigured monitor, producing overcranked colors. The longer answer to that is that you really have to read up on this stuff, including how transferring your work to mobile devices may already affect appearance by stripping away color profile info or causing color space conversions, e.g. if your artwork originated as CMYK. Rinse repeat for the actual upload to IG and their server-side processing. If you can provide a proper explanation of what you are doing we may be able to advise on where you are going wrong, but putting in a bit of time and learning a few things may not be a bad idea, especialyl if you plan on doing this more often...

Mylenium

Please forget websafe colors. They are a concept of the last century.

How is your color management set up?