e.g. Should I say the colors of tube 1-3
or the colors of tubes 1-3
?
I know there are more than one tube, but we usually say tube 1 and tube 3
and I feel strange to say tubes 1 to 3
.
Definitely a plural. Tubes is a plural, which allows you avoid having to say 'Tube' over and over again before each number. When you say 'Tubes', you are telling the listener that the numbers following each refer to a Tube.
So Tubes 1-3 is just a less annoying way of saying Tube 1, Tube 2 and Tube 3. Similarly, Instead of saying Tube 1 and Tube 3, you could say Tubes 1 and 3.
In mathematics, a similar thing happens with alegbra. You can condense the expression (xa - xb) to x(a - b).
Use the plural. You are speaking about three tubes (tubes one through three).
Tell me the colors of tubes 1-3.
I can't formulate a good expression to build a useful n-gram of this to see how common it is, but color itself could be in the singular as well:
"Tell me the color of tubes 1-3."
"Tube 1 is red, and tubes 2 and 3 are blue."