From a physically based rendering point of view, the problem you are running into is that Blender's HDR tone mapping is trying too hard to be helpful.
The effect you see in the reference image occurs due to blown highlights from a high dynamic range image being clamped to a low dynamic range. For example, the color
(300, 1000, 300) might be clamped to
(255, 255, 255), turning an unrepresentably-bright mostly-green color into solid white.
In Blender 2.8+, the default color management settings use Filmic tone mapping, which attempts to map HDR colors down to LDR colors in a way that preserves some sense of hue and saturation rather than just clipping out-of-range color channels to 255. This makes high-luminosity green still show up as mostly green in the final render rather than being clamped to white, unless you turn the intensity up really high.
There are a few ways of working around this to get the intentionally-blown-out effect you are looking for:
(not recommended) Disable the Filmic lookup table (LUT). You can do this by going to the Render Properties tab and, in the Color Management section, changing the View Transform from Filmic to Standard. However, this has a number of undesirable side effects. One such side effect is that there will be a lot of stairstepped pixels around the blown-out areas due to the unintelligent color clipping.
Change to a higher-contrast Filmic LUT. The setting for this is the Look drop-down, right under the aforementioned View Transform drop-down. Try switching from the default Medium Contrast to one of the higher-contrast Looks.
Turn the brightness of your emission material way, way up. It is easy to underestimate the dynamic range of light sources that exist in the real world. The sun is thousands of times brighter than typical indoor light. To compensate for this, you will probably also have to turn the density of your volume scattering way, way down.
This sample render uses a combination of methods 2 and 3. The file simply contains of a ring with colored Emission materials set to a Strength of 100, together with a world Volume Scatter with a teeny-tiny density of 0.015. The Look has been changed from Medium Contrast to High Contrast. I also set up AI denoising in the compositor to bring the render time down to a reasonable level on my laptop.
As you can verify with an image editor, the color of the ring itself appears to be
(255, 255, 255), but this is only due to the tone mapping being performed; in HDR linear color space, these values are much higher and more saturated, and this is indirectly visible through the scattered light around the ring and in the reflections on the floor.