Need Arduino Code

My son (7) wants to use a H-Shifter for his video game. I designed a 3D printable H-Shifter that will have buttons for each gear. The game has only two buttons to shift up and down. In the diagram provided the red led is to shift up and the green is to shift down. I attempted to code it myself, but I am running into issues. The yellow LEDs are to identify which gear is used so that when the button is pressed again it can shift down due to the yellow led being lit up, but I am new to coding for Arduino and unable to find the best method to code it. Any help on this would be greatly appreciated.