"By convention [or, “custom”], sweet; by convention, bitter; by convention, hot; by convention, cold; by convention, color; but in reality, atoms and void.64 (Democritus DK 68B9)"
This is in Philosophy Before Socrates Second Edition by Richard D. McKirahan.
"DK" refers to "H. Diels and W. Kranz, Die Fragmente der Vorsokratiker, 6th ed., Berlin, 1951 and later editions. The standard edition of the Presocratic Philosophers. Each Presocratic is assigned a number. The fragments of each Presocratic are also assigned numbers preceded by the letter “B.” Thus, the number for Heraclitus is 22, and Heraclitus’s fragment 101 is referred to as DK 22B101. Testimonia are likewise identified by numbers preceded by the letter “A.” The DK references are used widely in books and articles on the Presocratics."
So this quote above would appear to be a fragment directly from Democritus. This particular version has nothing that conflicts with Epicurus as far as I can tell.