Red and Black

Red, White, and Blue

Yellow, Green, and Black

Pink and Light blue

Purple and Yellow

Blue and Orange

Black and White

Examples of bad color combos

Green and Pink

Orange, Magenta, and Blue

Gradients

Multiple shades of brown or gray

Pink and Yellow

Gray along with multiple vibrant colors such as green or red

Thematic color combos
These color combos are often found in flags with a similar history/culture

Communist-Red and Yellow
Gran Colombia-Red, Yellow, Blue
Pan Arab- Red, White, Black, Green
African- Red, Yellow, Green
Belgrano- Blue and White

Bicolor and Tricolor, having your colors taking up equal spaces on the flag, either vertically or horizontally. Ex: France, Belgium, Poland, Austria

Side bars, and side triangles. Having a triangle or rectangle at the right or left side of the flag. Ex: UAE, Czechia

Diagonal Quartering and Bisecting. Bisecting is when a color of a flag takes up half of the flag in a triangle shape, ex: Anarcho Communism flag. Quartering is multiple colors take up 4 of the quarters of the flag as triangles ex: Jamaica

Stripes, Bands, and Nordic Crosses. Stripes are thin horizontal or vertical lines on a flag, ex: USA, Botswana. Bands are thin diagonal lines on a flag, ex: South Africa, Scotland. The Nordic crosses are the cross stripe design found on the Nordic flags, ex: Norway, Sweden, Denmark.

Stars: Stars can be any color, and can vary from from 4 to 5 to even 8 points. Ex: Australia, USA

Central design: A unique symbol in the center of the flag. Ex: India, South Korea, Canada, and my flag :).

Eagle/falcon/hawk: A bird of prey, usually found in European flags, can have multiple heads. Ex: Mexico, Holy Roman Empire, SPQR banner.

Islamic Moon: An Islamic symbol of a crescent moon and a small circle or star within the crescent. Ex: Turkey, Pakistan

Communist symbols: Yellow stars on a red background, hammers, sickles, etc are communist symbols. Ex: USSR, China, Juche Flag

Coat of arms. A royal coat of arms, often featuring a shields, swords and animals such as lions or eagles. NOTE: A good coat of arms is one that is possible to draw, if the coat of arms is so detailed that you can’t even draw it without taking hours, then it’s too complex. Ex of good coat of arms: Egyptian, Croatia, Slovakia, Slovenia, Hungary, Cyprus.

Flag shapes
Some flags make a different shapes from one another, this may make the flag stand out

Most flags are usually rectangular. Here are some common ratios for flag shapes:

1:2 ex:Nigeria
3:4 ex: Democratic Republic of Congo
2:3 ex: China
3:5 ex: Germany

Less common flag ratios:
1:1 ex: Switzerland
10:19 ex: USA
6:7 ex: Niger
11:28 ex: Qatar

Flag shapes:

Rectangular/Square, ex: Most flags

Pennon, a right triangle

Double pennon, the shape of Nepal’s flag

Slant, a rectangular flag with a right triangle cut off the end

Fanion, An equilateral or isosceles triangle

Burgee, The shape of the Ohio flag

Tassels, A flag with smaller strips coming off it, such as the Venice flag

Zamora, A flag with triangular “teeth” on the end of it

Swallow tail, A flag with an equilateral or isosceles triangle cut out of it.

Reverse swallow tail, A flag with an equilateral or isosceles triangle added to the end

Swallow tail and tongue, A flag with a triangle cut out from the end and a smaller triangle added into the middle of the cutout, creating 3 points on the end of the flag.
Design Sins
These are things to avoid when making flags

Text on a flag: NEVER have text on a flag, unless the text is extremely stylized and or small and hidden within a coat of arms. Ex: 90% of USA state flags

Flags within flags: Cmon man, don’t have flagception, it’s stupid. Ex: Australia

Too much of a design: Don’t spam a design feature everywhere, It makes the flag too complicated. Ex: USA flag, waaaaaay too many stars

Too many colors: Don’t use too many colors it makes the flag too complicated and “noisy.” South Africa is probably the upper limit to the amount of colors that you can have and still look good. A flag that in my opinion looks ugly because it has too many colors is the progress pride flag (the new pride flag)

Make things too detailed: It’s a flag, it needs to be recognizable from a distance, adding a ton of unnecessary detail ruins that.