Deciding Whether to Choose "を" or "と"

水が冷たいと言おうと思ったのに、水が寒いと言ってしまった。 I wanted to say that the water is cold, but I chose a wrong word, "寒い," to express how cold it is. ひろしはさやかに別れの言葉を言おうと思ったが、言えなかった。 Hiroshi wanted to say goodbye to Sayaka, but he could not.

The object of the verb "言う" is followed by either "を" or "と." In the sentences above, "水が冷たい" and "水が寒い" are the words that the speaker actually said. In such cases, you have to use "と." On the other hand, "別れの言葉" are not the exact words that Hiroshi wanted to say. In that case, you have to use "を."

(A) ひろしはさやかに、さよならと言った。 Hiroshi said "Sayonara" to Sayaka.
(B) ひろしはさやかに、さよならを言った。Hiroshi bid farewell to Sayaka.

The two sentences above are correct, but they differ in meaning. Sentence A means Hiroshi said the exact word "Sayonara." In the case of sentence B, Hiroshi did not necessarily say the word "Sayonara." He could have said "バイバイ", "じゃあね", "またね" or some other parting phrase. It can even mean that Hiroshi told Sayaka that they would never see each other again.