Spelling Challenges

Which is correct, grey or gray? I never remember.

Also, how about blond and blonde?

I also get confused with words ending in "ling" such as modelling and modeling, and travelling and traveling. I credit my childhood reading of books by British authors for this confusion in my mind.

I know that words ending in "or" often have a British spelling ending in "our", like color and colour, behavior and behaviour. And words ending in "ize" are spelled "ise" in Britain.

Speaking of British spellings, "tyre" always looks very British to me. :)

When I wrote my PhD thesis many years ago, I was describing thin metal plates (called diaphragms) with groves on them forming an "X" that burst along the grooves when the pressure differential across the plates exceeded the strength of the remaining metal in the grooves. Being a bike rider, I used the word "pedal" to describe the four flaps that opened. An astute reviewer pointed out that the flaps were named after the parts of a flower (i.e., "petal") and not the parts of a bicycle. A natural confusion for me, because my American accent does not distinguish between a "t" and a "d" in the middle of a word. For example, I pronounce metal and meddle the same. I do not, however, pronounce "tent" and "dent" and "tend" the same. I wonder why?