The yellow one looks to be a combination of Ragwort, Gorse and Scotch Broom, with the Gorse being close up there with the hound jumping around in it. It's not great for livestock, but is harmless otherwise, and in Ireland is fairly easy to control. So easy, we don't need to bother. Ragwort will look much different in a few months as it blooms later than the broom does. Ragwort also prefers it wetter, as well as Gorse (yes, it gets more wet here than what's in the video). Of the three, we have much more Gorse. Ireland is rather late blooming compared to the states. Late May is considered middle of spring here to some species.
Broom is native to Europe. It doesn't grow nearly as fast here as it does stateside due to the competition it has with local flora and fauna, especially grass and ferns, which are much more aggressive here in Ireland in moist regions. Scots/Scotch broom prefers sandy, well drained alkaline soil - which does not describe most of Ireland and much of western Europe, at least not at altitude. And it likes sunlight(which usually also means a plant likes it warm as well) - so it struggles in Ireland, whereas the grass here grows year round. It is usually found here near rock outcroppings(which makes it easy to survey the land from a distance here). So on the barrens, and up in the mountains is where it is usually found. This video is taken near the PowersCourt Waterfall, so it is actually up in the mountains, which is why you see a lot of it here near the rocks.
I tried to find other photos I might have had of it, and in the thousands of photos I have of Ireland, I couldn't find one good example. So it is actually fairly rare here outside of the top of our mountains. The most I have ever seen of it in person is near Hollywood, Wicklow, which is very rocky. Here's a photo I found on line as I do not have one myself. Even so, as in the video, much of this is Gorse:
You can see in that photo it is sticking to the outcroppings and leaving the meadows alone. Still, there's loads of it there. The photo makes it look smaller than it is. And even so, that pinkish stuff you are seeing is dormant fern. So even on the hillside, it competes well with the gorse etc. And this is kind of a desaturated photo it appears. There's still loads of grass about.
Here's a couple of views from above Glendalough from behind the Sugar-Loaf peak in the distance. This is all at roughly 1,000'-1,500' altitude, and you can see even here it's just too wet for it to take hold even though there'd be plenty of rocks here still:
Also, if you have grazing land that gets plenty rainfall(which describes 99% of Ireland), the animals(via trampling and urinating) and water keep the broom away without any management necessary. The scene in the video is managed only by allowing sheep to graze on it and people to hike on it. Which, unfortunately leaves their droppings everywhere(prolly both people and sheep!), so watch your step, and don't let dogs eat it because they will eventually get luke worm.