1. Center bar:
Middle row, cols 2-4 = positions (3,2)-(3,3)-(3,4)
This can be rotated to vertical or reflected, but always stays at the center.
2. Off-center:
Top row, cols 1-3: (1,1)-(1,2)-(1,3)
Top row, cols 2-4: (1,2)-(1,3)-(1,4)
Top row, cols 3-5: (1,3)-(1,4)-(1,5)
But these are all equally distant from their accompanying edge; by symmetry, place (1,1)-(1,2)-(1,3) is same as (1,3)-(1,4)-(1,5) under reflection.
So for each "run of 3" not at the center, there are only two types by distance from the edge: edge and one-step-in.
So per orientation, horizontal and vertical, that gives:
Center
Edge
One in from edge
But rotations mix horizontals and verticals. So these three types exhaust the possibility for straight bars:
Case 1: Centered three-in-a-row (middle row & col)
Case 2: Edge three-in-a-row (either on top/left or bottom/right edge)
Case 3: Offset three-in-a-row (one away from edge, but not center)
Centered bar: ((3,2)-(3,3)-(3,4)) (also ((2,3)-(3,3)-(4,3)), rotated)
Edge bar: ((1,1)-(1,2)-(1,3)) (can be rotated/reflected to any edge)
Offset bar: ((1,2)-(1,3)-(1,4))
So 3 distinct orbits for straight bars.
B. Diagonal Bars:
Now, consider the diagonal three-in-a-row:
((1,1)-(2,2)-(3,3))
((2,2)-(3,3)-(4,4))
((3,3)-(4,4)-(5,5))
Similar situation on other main diagonal.
Only possibilities for "bar on a diagonal":
Main diagonal, centered
Central run: ((2,2)-(3,3)-(4,4))
Main diagonal, edge
Edge run: ((1,1)-(2,2)-(3,3))
((3,3)-(4,4)-(5,5))
The two runs at the ends of the diagonal are symmetric by 180° rotation.
Similarly, diagonals above/below the main diagonal, but only have length 3.
Also, shorter diagonals: length 3, only one way to pick three in a row.
But are these different up to symmetry? For a 5x5, all "sloping" bars at the edge are the same under symmetry.
Diagonal (main): Centered and edge.
And diagonal bars not on the true main diagonal or true anti-diagonal can be rotated to each other.
So, just as before:
Diagonal centered
Diagonal edge
So, in total, for "three-in-a-row" on a diagonal, we only get two types: centered and edge.
In conclusion, there are 5 distinct types of three-in-a-row colorings (orbits under symmetry):
Final Answer;
\(\boxed{5}\)
There are 5 distinct colorings of three squares in a row (of any direction) in a 5 by 5 grid, up to rotation and reflection.