The tertiary colour here is blue. (Red is primary, and green secondary.)
...The tertiary colourMost people know that you can pick a primary and secondary colour in Paint - primary is left-click, secondary is right-click. But did you know there is a tertiary colour controlled by CTRL+click?
In case you didn't guess, this means that you can use the tertiary colour to paint by holding CTRL while click-dragging the cursor in whatever tool...
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