You can almost tell how long a sailor has been sailing by the color of the lines on their boats, whether it be in threads like this or walking the docks in my marina.
Life long sailors don't bother with colors for lines. Newer sailors, like myself, seem to like having colors. The newest sailors seem to like red on port and green of starboard.
As
@Stu Jackson taught me early on, YBYC. (Your Boat, Your Choice)
My sail control lines are of various colors. When I bought any first keel boat 12 yrs ago I found it helpful to have different color lines and my (now ex) wife liked the pop of color they brought to the all white boat.
In fact I still like the "Bling" of new brightly colored lines I see on some boats.
Now, with a boat that has something like 8 lines entering the cockpit through the dodger, I find it helps to keep lines sorted, especially for my wife who is new to sailing.
I also find most non sailing guests have fun helping out when tacking. Much easier for me to ask them to pull in or let out the solid blue line then grab the white line, no the other white line.
As to what colors, when I outfitted my C30 the first season in 2018 I tried to group main sail lines with blue colors for the sheets, halyards and traveler. For the jib I used green lines for the halyards and sheets. Other trim control lines were variations of red.
It's hard to stick to a color plan though. As I've upgraded/added some lines I couldn't find them in the color I wanted.
@outatime If you do a Google search on "what color lines for my sailboat" and find many results, several pointing back to this forum.