as helz said red is a very hard colour to get a match with, probably the hardest out of every colour. if you buy the correct colour for your car it will almost certainly be a noticably darker shade. red fades very quickly. how much yours has faded will depend on age, amount of time in the sun, and how often the car has been polished and looked after throughout its life.
depending on how faded yours is i suggest you get the correct paint for your car and then very careful add drips of white and mix them in until it mixes to the correct colour of the car. the last time i did this i had to repair a 1998 escort. the red paint required a 5% mix of white adding. that was very faded. i doubt you will need to add that much but it depends. just add slowly, and compare a blob of paint dried onto a piece of white card next to the car in direct sunlight when matching, the wet paint will usually change colour slightly when it dries. a blob on some card will dry quick allowing you to see how close a match you have
