My name is Sarah, I'm on the Vue core team and do a lot of work with Vue and SVG animation using GSAP. Yep, you're on the right track, refs are the way to target these elements though technically it still works to target an id or class as usual. However, there are some key pieces in here that I want to separate out in case it's helpful to you, because really the sky's the limit! And they play so well together:
1) The way that animation and rendering work, you are *always* going to be touching the DOM in the case of animation, this can't only happen in the virtual DOM (something that people miss about React, too, even when looking at libraries like React-Motion)
2) There's a way to interpolate numbers that then update the DOM by transitioning state, and then there is accessing the DOM directly. You can use Vue and GSAP for both. I rewrote the docs example to use GSAP for our transitioning state example here: https://vuejs.org/v2/guide/transitioning-state.html#Animating-State-with-Watchers, but the way you're working with the DOM nodes and watchers, you may be more interested in this chart I wrote with where I'm spinning up SVG DOM nodes with directives, which is similar to what you're doing. In other words, you can use Vue and GSAP to interpolate number or values, and then apply that to a style binding, OR you can just update the fill in GSAP by targeting the element directly, that will still work. There is even a relative HSL tween that gsap offers if that's your jam
4) You can also plug directly into the mounted lifecycle hook, as you can see here: Vue Weather Notifier Pen. This way you can activate an SVG animation on the component as soon as it's in the DOM. You can also see in this pen I'm changing opacity, using drawSVG, changing color, rotating, you name it- it's all possible on SVG elements and you don't *have* to put them in data. Though there's nothing wrong with transitioning state that way either.
I also wrote this article that should help you: https://css-tricks.com/intro-to-vue-5-animations/
And have this open source repo which is a whole workshop just about vue and svg animations: https://github.com/sdras/animating-vue-workshop
Please feel free to ask any questions as well. Thanks!