Darell has 3 meters of colorful string. He uses 75 centimeters to make some bracelets. How many centimeters of string does Darell have left?

First, we need to convert 3 meters of string into centimeters. Since 1 meter is equal to 100 centimeters:

\[ 3 \text{ meters} = 3 \times 100 \text{ centimeters} = 300 \text{ centimeters} \]

Next, Darell uses 75 centimeters of string to make bracelets. We can find out how much string he has left by subtracting the amount he used from the total amount of string he had:

\[ \text{String left} = \text{Total string} - \text{String used} = 300 \text{ centimeters} - 75 \text{ centimeters} \]

Calculating this gives:

\[ \text{String left} = 300 - 75 = 225 \text{ centimeters} \]

So, Darell has 225 centimeters of string left.