In British English, the word colour is spelled as color.Are these sentences correct?

[scott833]

1) In British English, the word colour is spelled as color, whereas in American English it is spelled as colour.

2) My three years old spelled the word cat as kat.

[5jj]

1) In British English, the word "colour" is spelled as "color", whereas in American English it is spelled as "colour". You have it the wrong way round - BrE has the 'u', AmE doesn't.

2) My three-years-old spelled the word "cat" as "kat".

More natural for me would be:
Colo(u)r" is spelled/spelt with a 'u' in British English and with no 'u' in American English.
My three-year-old spelled/spelt the word "cat" with a 'k' (instead of a 'c')
My three-year-old spelled/spelt the word "cat" K-A-T.