It depends. It's best for you to try them all and judge yourself.
Reds are very easy to type on. If you jump from rubber dome to reds, you will notice how you just hammer the keys into the keyboard. They are very easy to type on for a very long time, since their actuation is around 40g. They are called linear (no bumps and no clicks) switches. There are reds and blacks (60g) that are linear. Blacks make you feel like you type on a small pillow. It's like red but you won't bottom it out necessarily. It will also make your fingers stronger and make you type faster.
Blues and Greens (50g and >>65
g actuation force respectively) are clicky switches, meaning that each time you press on a switch, there is this audible click that you can hear and it lets you know that you have went beyond actuation point and the signal occured, so that your letter is now typed on the screen. It's harder than linears, very loud, so if you have it in the office people will seriously think that you brought a typewrite and/or will get annoyed fast, especially if you type 100+ wpm. Green switches are a lot harder to press, however they will make your fingers stronger and you will type faster as a result. It will also improve your endurance so that you can type on lighter switches for much longer time.
Browns (45g actuation force with a bump, but no click) are neither linear nor clicky. They are a class of its own. Instead of a click, they have a slight bump that you can feel when you push down the switch. It's actuation force is slightly higher than those of reds. Most popular switches on the market are Red, Blue and Brown. Blacks, Green, Grey and white are hard to come across.
Btw all the text above is for the Cherry MX switches. Since their patent expired there are a lot of chinese knockoffs that have similar colors or even different ones, but their actuation forces can be different along with the lifetime of the switches. The most popular ones are Kailh and Gateron switches