Hey guys, I'm new to forums in general so let me know if I'm missing some etiquette or need to fix something, but this seemed like a really good question and I wanted to throw in my opinion, it's nothing new but still fun to share. The TL;DR version is I like all of them equally as far as what the have to offer (although I'm not too keen on Red), and if you're blending them green and white work best for me personally. Individually though they have too much to offer to pick just one.
White: Probably the colour that I'd play if I only had to choose one. So many options, and everything seems fair.
Serra angel holds a spot in every long time player's heart I think. White has always been good and a few times I think it has been the best, from control to stand-out creature White always offers something even if it's overlooked. I feel like it's a
rite of passage as a Magic player to start with a White or a White/Green deck. Everything makes sense and you feel like you get fair value from every creature or spell, and what do Magic players love more than value?
Blue: MORE VALUE, the only thing Magic players love more than value is something with MORE value. That's what Blue offers. Mono Blue Merfolk is my favourite deck to play because Blue offers you something that a lot of other colours don't: Free counterspells! And how can you say no to free? Blue has had the most format shaping cards, and in Legacy almost every deck will splash Blue if given the chance. I think the more you grow as a magic player the more you come to appreciate what this colour offers you.
Black: Very much related to White, but on the opposite side of the spectrum. Where White will offer a your opponent an upside (
Swords to plowshares will
exile a creature but also
heal them,
Path to Exile will
exile but give them a basic land) and that's considered fair, Black will hurt you and that's considered fair (
Thoughtseize deals you damage,
Dark Confidant does the same). Black will win at all costs and that's why it's such a good combo colour. It's literally win or die trying!
Red: I really don't like burn, bu at the same time red is so good it's a shame that my first thought is negative!
Splinter Twin owned an entire format after all! Yes many red cards are owned by
Leyline of Sanctity, but you know what? Reanimator dies to
Leyline of the Void and no one gives it the same type of bad reputation. I think Red is the most useful colour in conjunction with another. Blue/Red Delver ROCKS, because it's a Burn Deck that will also out Aggro you. Small Zoo has beat my (Modern) Merfolk deck 2 weeks in a row at my local Meta, I have huge respect for Red but I think that it's at its best when used with another colour.
Green: MC Hammer loves this colour, so do I. I feel that this is the most honest colour, probably the most tricky thing you can do with Green is a few combat tricks to boost your damage in between Declare Blockers Step and Damage. But nothing feels better as a new player than Mana ramping and playing a HUGE creature that your friends have no way to deal with (luckily when I was starting out me and my friends never knew about Doomblade or other cheap removal, the most effective thing was to have a bigger badder creature!) and I think that's something all Magic player like. Having a creature so big their opponents don't know what to do but say a prayer as they try and topdeck an answer.
Colourless: I had to add this,I mean Modern is currently owned by Eldrazi so Colourless (Generic? Waste Mana? Purple-y Diamond stuff?) is certainly a "Colour" on its own now. MUD or "Robots" and Affinity have also been long-term staples that deserve a mention. I don't have much experience with colourless decks, but I will say that this is the category with the most "bombs" in it.
Ugin the Spirit Dragon,
Blightsteel Colossus,
Karn Liberated (just to name a few).