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There are 4 balls in a bag. 3 of them are green and one is red.

1) What is the probability of randomly taking out that one red ball? 2) What is the probability of randomly taking out a green ball?

I have two solutions in mind but i don't know which one is correct. For the first question i think that the probability is 1/4(because there are 4 balls) and the other solution for the first problem i think could be 1/2 (because there are only two kind of balls green and red). I would like to have an answer for both questions.

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    You are correct about the first one, but not the second. Hint. Suppose the balls were labeled $G_1,G_2,G_3,R$. Now, each of these has a $\frac 14$ chance of being the one drawn. What can you conclude? – 2017-02-07
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    You can easily find out which of the solutions is right, by applying it to the lottery. Your second solution then reads: "There are two possibilities, either I chose the right numbers, or I didn't; therefore the probability of winning the lottery is $\frac12$. Does that sound right? – 2017-02-07
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    @celtschk - Are you saying that the solution is 50% because there are only two colors? – 2017-02-07
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    @L.B: No. I took the lottery example because I thought there the conclusion should be so obviously wrong that you'd notice it. Do you really expect to win the lottery every second time? – 2017-02-07

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Your first solution is correct since in random selection we can't distinguish colours and all balls are alike.