Green [Fluent in 10 Languages]
- you get to choose which languages (in addition to any you can already speak/read/write fluently)
- fluency extends to speaking, reading and writing
- your expertise in your 10 new languages would be equal to the level of your current day most proficient language and you would be able to improve upon them as normal
- the languages are bound to human languages (you can't choose speak with animals)
This was my first choice, and i still thing it's a really strong one.
Leaving aside interesting possibilities as ancient languages, this is still an ability which not only is very cool and handy to have, but that can also grant you a living.
There's really no downside in being able to master 10 (11) languages. It's only a matter if other potions could give you more.
Blue [Bangin' Bod]
- your body is transformed to the level of a "9 or 10" in line with the beauty standards of a culture of your choice (but still bound to the limits of reality... you can't look like the Hulk from the MCU for instance)
- you gain no other benefit (increased strength, endurance, vitality, lifespan, etc.) beyond your physical appearance (although you can still improve upon these traits in the exact same way as you would without the potion)
- to ensure that the Red potion is not completely redundant, your appearance is still bound to your age. Meaning, if you gathered 100 people of your age, you would be consistently rated to be in the top 10 among them in terms of physical appearance. So if you're 80 years old, you ain't beating out a good looking 20 year old.
- your bangin bod includes your facial appearance
- everyone you knew would still recognize that it is you (for the sake of simplicity), you're just more aesthetically pleasing
- you retain your bangin bod despite potentially poor lifestyle choices, but you can still accrue negative health benefits
this could grant you a living. Naomi Campbell falls in this cathegory, i believe.
Anyway, you just look nice, that's all your advantage… you still have to rely on your charisma and intelligence / knowledge, so the real advantages are kinda limited.
Given that i was never fixed on physical appearence, and i don't care if in the same room there's someone prettier than me, i won't drink the potion
Black [Mind Reading]
- you have the ability to choose when and on whom you use your powers on (you have full control over it)
- you have no ability to control someone's mind directly (although, with practice, the ability to read another's mind could make you very persuasive if you are clever enough to exploit it)
- reading someone's current thoughts requires the same mental concentration as listening to someone speak and understanding them
- reading someone's past thoughts requires greater concentration (something along the lines of doing conventional research and shifting through information)
- as a frame of reference, think of Charles Xavier from the X-men but without the power to control/influence the other person (the information only travels from them to you... you can't implant thoughts/ideas)
It's a solid power. Useful, strong… can definitely help you in making money. Big money, and power. The downsides are limited (for example to know secrets or opinions that whould have been better to remain hidden) and the possible gains are kinda high.
However, I do believe that, in the long time, it could be very stressful. The temptation to know the hidden thoughts of (for example) your wife…
Red [Look 25 until you die]
- your appearance falls within the upper and lower limits of what you could/did look like at the age of 25
- you are still bound to conventional weight gain/loss and muscle gain/loss
- drinking the potion does not alter your life expectancy
- you gain no further advantage beyond looking young (no increased strength, endurance, vitality, lifespan, etc.), you still physically age as you would if you had not consumed the potion, you just don't look it
Seriously? I will just look 25, but i will have the bones ache of a 60 yo?
what's the advantage? at this point, it's 100 times better the Blue potion, hands down.
Anyway, just to be clear… even if you could keep the endurance and the physical advantages of a 25 yo person, that would still be a trap. Do you really want to be a 25 man, married to a 60 woman? Do you want to explain to teachers (or doctors) that you really are the father of that 14 yo girl? Or that you really have the age to get a pensioner concession card?
That's all the downsides of Highlander, without any of the advantages.
As actually written, I would fight to spit this potion, if someone forces me to drink it.
Purple [Able to eat anything without gaining a pound]
- your fat levels remain at an ideal/healthy level no matter what food you eat and in what quantity
- you are still able to gain (and lose) muscle as normal
- you do enjoy the health benefits of living at a healthy weight
- you are not immune to secondary effects of a really poor diet (clogged arteries, vitamin deficiency, etc.)
- consuming too few calories will still result in weight loss (and any associated negative effects), but upon increasing calorie intake above expenditure you will gain weight back up to that perfect ideal (but no further)
That's not bad but… really?
Basically, I can eat as much as i can, without any
visible negative side.
Please, unless you suffer from something that actually makes this useful (excessive metabolism, so you become fat just by eating a slice of bread), then how this is a so big gain? I am 50, height 1.83 m, 80 kg. I eat what i like without feeling the need to choke myself on a whole cake, and a portion of lasagna is enough. What the gain in the ability to eat 3 pizzas in a row? that i spend triple as much in food?
And anyway, you won't be immune to the effects of a poor diet, so you can easily die in a short time, because you won't even notice the damage you're doing to yourself.
BUT even if you would be immune to diseases caused by a poor diet, there's still a high chance that eating will become your hobby. wow.
in the end, my personal preferences:
1) green: good, no downsides
2) black: the best upsides, but possible unknown downsides
3) blue: limited upsides, no downsides
4) Purple: limited upsides if you naturally tend to be a fat person, possible heavy physical downsides.
5) Red: false upsides, heavy social downsides
. Poker anyone? 
Realistically you could dominate nearly any field...
