Tulip Flowers Have Mutated to Yellow

Is it my imagination or do tulips revert back to yellow like other flowers? I’m trying to get different colored tulips to grow, but it seems they last for a season or so and then come up yellow again.

Many of the newer hybrid tulips are short lived. They put on a fabulous floral display for several years and then produce greenery but no flowers.  It is possible as the hybrids stop blooming your older species or perennializing tulips are growing and multiplying and stealing the show with their yellow blooms.  Or the other colored flowers may have mutated to yellow.  And a less likely possibility is your hybrid tulips were able and allowed to set seed.  After several years the seedlings developed into flowering bulbs that were different than their parents, in your case, yellow.

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