Here's what rhymes with pastelblue.
you true blue drew u blew lieu lu rue brew loo pew yew yu ewe ru roux to who do two new through too few view due knew du grew que crew threw coup flew q qu shoe zu clue cue dew glue hue queue shew su sue tu vous chew cu deux flue fu slew untrue zoo bu flu hu ju jus ku mu nu peu piu pu seu shu sou thru vu woo boo chou chu coo cou doo feu fue gu hew mieux shou shrew sprue thu tue tzu vou vue wou wu clew goo mew moo pooh strew poo shoo spew gnu slue thew whew phew review pursue screw anew renew accrue debut stew taboo adieu ado skew tattoo beaucoup outdo revue askew imbue outgrew redo halloo valuer endue fondue indue bestrew booboo regrew achoo into withdrew bamboo canoe undue ensue retinue subdue undo construe jusqu barbecue eschew sinew vnto ballyhoo hullabaloo barbeque bugaboo foreknew zebu kazoo buckaroo muumuu prevue superglue overdrew wazoo atishoo interview revenue overview residue avenue rendezvous caribou overdue overthrew shampoo overdo honeydew marabou peekaboo overflew overshoe overgrew hitherto kangaroo cockatoo misconstrue