If you are talking about the color, you can say ่่ฒ (lan2 se4). The word ่ฒ means color, so saying this phrase refers to only the color.
- ไปๆๅๆฌข่่ฒ (ta1 zui4 xi3 huan1 lan2 se4): he likes blue the most
If you are talking about a blue _________, using blue as an adjective, you would simply say่ (lan2), or่็ (lan2 de1)
- ไปๅคฉ็ๅคฉ็ฉบๅฅฝ่ (jin1 tian1 de1 tian1 hao3 lan2): Todayโs sky is so blue
- ่ฟๆฏ่็ๅคฉ็ฉบ (zhe4 shi4 lan2 de1 tian1 kong1): This is a blue sky
