Tan is darker than beige. They are close in color. Beige is a pale sandy yellowish-brown color. Tan is more brownish.
TAN: The shade of tan is literally the colour you get your skin slightly burnt under the sun. It is a darker version of beige. It can be called pale brown. You can make out the difference between the two colours easily if you compare them. Tan is a colour which has a yellow undertone to brown.
The color tan has hexadecimal color code #d2b48c. It is 82.35% red, 70.59% green and 54.9% blue with an approximate wavelength of 579.64 nm.
BEIGE: Beige is a much paler shade of colour. It is halfway between white and crème. Well, that is what you call beige. Though it has got a close association with tan, you can still make out between them. Beige is slightly lighter than tan. It has got an orange undertone to brown. Beige is a colour highly suited for making formal dress materials or even formal shoes of women.
There are shades like beige, tan, ivory and a lot more. For example, to get the dewy look that is very popular nowadays, you use the tan coloured foundation with a nude lipstick. That nude lipstick is what beige is. So basically, you get the application of both the colours on one skin tone.
It is difficult to identify the exact shade of colours at times for their close association with one another, but you can always go for comparison with shade cards which are easily available online nowadays. The shade of light brown when mixed with any shade can give a different colour. We have the mauve, taupe, ivory and a lot more which are basically undertones of different colours mixed together.
Tan and beige are close, the main difference is tan is darker.