Before you go ahead and change into a redhead, make sure you have both the wardrobe and the makeup that you will need. It is amazing how changing the color of your hair, particularly if it is quite a big change, can so totally alter your overall appearance that you actually do need to wear either a different style or different color clothing. The same holds true with makeup as well.
Starting off with your foundation, try to avoid ones with a red or pink base. You should try to use one that is as close to your actual skin color as possible. Do not think, now that you are a strawberry blond, that you should have a very pale complexion. Sticking as closely as possible to your natural coloring is always the best. So buy foundation that is the same shade as your skin with maybe a peach or yellowish golden tint to it.
As far as your choice of eye-shadow, you should probably stick to the earthy colors. Steer clear of baby pinks and baby blues, they really do not go at all well with red hair. Browns, plums and greens always look great on redheads. One small point that is often overlooked is the eyebrows. If you become a redhead you should also probably either dye or bleach your eyebrows. Alternatively you could also just buy an eyebrow brush and color them a lighter color if you can.
As with eyeshadow, avoid pink lipsticks. Usually you should match your lipstick to your blush and vice versa. Red usually does not look that good on redheads either, unless it is a brown or brick red. Peach or apricot shades are good, anything with a touch of gold looks great. Once you find a lipstick that really matches with your hair color, you can rest assured that it will also be the perfect blush color.
When in doubt about what colors look best on you, you could always talk with a beautician and see what they recommend. Alternatively, look through different fashion magazines and when you find someone with the same colored hair as you have, look over their make-over and see if you can match it or at least get some ideas.
The main thing to realize is that if you do end up changing your hair color, especially if you become a redhead, you will most likely need to change your makeup as well.