Tonal value is something we all struggle with to an extent, yet is so very important! Colors tend to be very distracting especially if they’re a “bright” color, so actually seeing Tones is difficult.
It dawned on me the other day, as I was squinting, trying to see tones, I could take a picture of my Soft Pastels, use my phone and change it to Black and White! Wallah, tonal value! Just be sure to not adjust the brightness, just switch it as is.