Working in colour has been trickier than I had expected. Colour matching requires not only mixing the right colour/hue, but also the right value (i.e. relative darkness or lightness in the overall scheme of things) and the right chroma (colour intensity).
On average, I currently get about half my colours right in every painting - and the only way to learn is to keep on mixing (a lot!)
When trying to colour match, you will quickly learn that most colours we see are not a colour that comes straight out of the tube. It is often necessary to mix three or four different colours - and in the right proportions. Get the proportions wrong, and the colour may change completely, especially with colours that have high tinting strengths.
Old Holland's English Red (PR101) has tripped me up on several occasions - it's one of those colours where a little goes a very long way!
I have always been taught to use white to lighten a colour. I have now been made aware of two further option: Old Holland's Schevingen Yellow (which other manufacturers call "Winsor Yellow) tends to keep a colour's chroma; Old Holland's "Naples Yellow Extra" maintains a warm undertone.
I was concerned about using Naples Yellow because I had read that it is toxic. The pigment database I had been introduced to on a workshop came in handy. The database not only lists the properties of each pigment and any potential issues, but also the different names manufacturers use - manufacturers may use the same name for very different pigments. I found out that Pigment PY41 (Naples Yellow) does contain lead... However, Old Holland's Naples Yellow Extra is a mix of 2 whites and a yellow ochre [PW4 (Zinc White) + PW6 (Titanium White) + PY42 (Transparent Yellow Iron Oxide, Yellow Ochre)]... Manufacturers also use different names for the same pigment - Old Holland's Schevingen Red is for example also known as Naphthol Red.
There is a lot to learn!
I usually do not play games on my phone, but I have found the game "I love hue" helpful in learning more about the world of colour.