Auto select Radio Button Option

Auto select Radio Button Option

Hello,
Hope someone can help.
I would like to know how to auto select a Radio Button option in one field based on the user input of another Radio Button Field.

For Example, if the first radio field (colour) had the following options:
Red
Blue
Green

and if the second radio field (shape) had the following options:
Square
Circle
Triangle

What script do I use so that if the user selects "Blue", from the first field, the second field automatically selects "Triangle"

?