In terms of physiology, the color is stimulated in the brain when the eye reports input from short wave blue cone cells along with a sub-sensitivity of the long wave cones which respond secondarily to that same deep blue color, but with little or no input from the middle wave cones. The brain interprets that combination as some hue of magenta or purple, depending on the relative strengths of the cone responses.
In other words, our brains are like “🤷♂️, here’s a thing”
You will speak the version that you learned. You will mostly notice regional differences in the idioms and synonyms of the words you know might be used more commonly in one region vs the other.
For example, in London you might hear people use boot instead of trunk.
But the majority of the words will be the same regardless of region.