------
## 最终结论
```python
def group_keyvalue(pairs):
    result = {}
    for key, value in pairs:
        if key in result:
            result[key].append(value)
        else:
            result[key] = [value]
    return result

# Test cases
assert group_keyvalue([('yellow', 1), ('blue', 2), ('yellow', 3), ('blue', 4), ('red', 1)]) == {'yellow': [1, 3], 'blue': [2, 4], 'red': [1]}
assert group_keyvalue([('python', 1), ('python', 2), ('python', 3), ('python', 4), ('python', 5)]) == {'python': [1,2,3,4,5]}
assert group_keyvalue([('yellow',100), ('blue', 200), ('yellow', 300), ('blue', 400), ('red', 100)]) == {'yellow': [100, 300], 'blue': [200, 400], 'red': [100]}
```